hi Diana,
I'm really sorry you're having such troubles. I can hear your pain and discouragement in what you write. I hope to offer you some practical suggestions for turning the relationship to a more positive and even enjoyable one.
In spite of all the tension and troubles, i do think it's possible to turn things around. Your husband says he's thinking of divorce but look... he's been hanging in for some time, so he does love you and he is trying. He's been willing to do counselling, so he cares about saving this. He obviously cares that you are happy. Wow. That's actually a LOT. Marriages have been saved on a lot less. So the question is, are you willing to make the changes it takes? This isn't a matter of blame... i'm not suggesting you take steps because you're at fault or more at fault... you aren't. But two of the things that often stops us from solving ANY problem are excuses and blame... something i try to remember in my own life. Both of those things stop us dead in our tracks from doing what we might do to solve things, and if you look at any persistent problem in anyone's life, you are likely to find those two running amok.
The reason i'm going to suggest things you can do, and not your husband, is only because we always begin with ourselves, k? So no more figuring out if it's your fault or his fault... that's definitely not going to make things better, so that's something you need to set aside. Permanently! The blame game will send you to divorce court. Instead always think of things you can DO to make things better, and things you can ask if he's willing to DO, k? You can't steer a car if you're looking out the rear view mirrors... you need to shift from where you've been looking to where you would like to go! Got it?

First i would ask yourself, are you willing to put in effort and are you willing to do things differently? Take your time with this question, because if you are not really committed, things are likely to remain difficult or get worse. You know what they say... do the things the same way and you'll get the same results!
Second and third, whatever the past, whatever the "analysis" of the present... you are going to do two things. You're going to be committed to
listening and you're going to be committed to
communicating with your end in mind. Listening comes first. The number one trigger for infidelity and in many cases divorce is lack of emotional intimacy... not sex... but simply lack of feeling connected. Surprisingly, guys especially need this. I'm sure you know you need this, too. Your husband needs to feel heard. Are you willing to listen and not shut him off, interupt, walk away, are you willing to interact and try to understand him? You need to do this every day, as much as possible. Start asking him questions related to what he is communicating. If he says he doesn't like how you discipline his children then try not to rankle and ask how you can do it a way he likes. I didn't tell you this will be easy, but making things better will require the two of you working better together, right? Getting on the same page? So, you have to understand where he's coming from, what he wants, and what he needs for things to get better for HIM.
You also need to be able to communicate better yourself. How much of your communication now with your husband and your husband's children is negative? ...fighting, orders, etc.? Aha. Yes... this usually happens when we're unhappy and when we're having relationship troubles! It's important to communicate in these areas of conflict, but it is also vitally important to start communicating fun, enjoyable, positive things. Right now the boat is tipped waaaaay to the negative, yes? See if you can start establishing some enjoyable routines... asking your husband how was his day? Maybe setting up a date night once a week or start doing again things you shared and enjoyed together while you were dating. Talk about things like movies, books, the weather, your friends, etc. Go for a walk together after supper... it doesn't matter, but find some positives. It will also help with your depression. No excuses! I know you're tired, busy, etc. But this is simply what it's going to take to be happier and have a happy relationship. You won't get to where you want without it, so it's more important than it seems. And start communicating what you APPRECIATE... tell him what you like about him. Tell the kids what you like about them. Tell anyone what you like about anything, the taste of supper, whatever. You have to start shovelling out the negatives from your life and some from the communication... there is way too much of it and it's weighing everything down in your life. The other important part to your communicating is to figure out what you really want, what would really help you, and communicate these things in short, clear, repetitive ways... but ways with your outcome in mind. Saying something in anger is understandable, but it's unlikely to get the results you want as well as communicating it without hurting the other person, would you agree? Name calling, criticisms, etc., just don't tend to get good results. So do you want to get in a good one, or do you want to get results? This is how you have to start thinking in your communication. Opening up and letting others know what's going on inside you will help. If you feel afraid to talk with your husband because of the response you might get, then gently let him know that. You could even say, "i'd like to share something with you, but i'm afraid i'll get criticized or get a quote, ...can you just listen this time?" or something like that. Think you can change some of the way you've been communicating now? Make it more positive? Listen more? Remember... you want positive results, right?
The last thing i would suggest concerns the blended family. I know it must have a lot of challenge in it. Kids start getting raised one way, and then have basically a new parent who does things a different way. This gets confusing and raises conflicts. I think it would help if you and your husband talk privately once in a while to get on the same page about how to raise ALL the kids with no distinctions... so that there are the same rules for everyone, and being given the same way by you and your husband as much as possible. Keep the rules simple and few. Discuss with your husband areas that you can make decisions with your step kids and ones where they need to ask their father. Gradually, as trust builds, you can gain back more influence, but for now, just try to seek agreement with your husband concerning the kids. And i do really think it's very important that the rules are consistent across the board!!!... meaning ALL the kids, and BOTH parents. If his kids have to ask him before going out and not you, then your kid has to ask you and not him, etc. Any imbalance will come back to bite, so really try to eliminate these inconsistencies. Be willing to bend on your kids too, so that you can find agreement and consistency for all. Second, everything that applies to your husband about listening and communicating, ALSO applies to his kids! You need to get some positive time with them, appreciate them, listen to what they are trying to communicate, and communicate what you feel and need from them, in a positive way. It will help foster their respect for you, so this is for you, too.
I know all this is asking a lot for you to change. But this is simply a matter of what is it going to take? Blame and fault finding and rationalizing why you're doing things the way you are now, simply will NOT solve the relationship problems. You will not be doing all the work of fixing these relationships, but you need to quit concerning yourself with how you want them to change and instead start focusing on what YOU can do and need to do to make this better. If you change, they will jump at the chance to change in a more positive way, trust me. They are probably just as unhappy with the way things have been and they want to get this into a better place too. And they DO want you to be happy... think of that as a treasure, because it is. Your husband wants you to be happy. You know what that is? That's love!

Can you see how these things fit together? Commitment to change -listening - communicating positively - appreciating others - same rules for everyone. Remember to focus your time, your words, your actions, everything... on where you wish to go and not where you've been. If a comment on your lips is a criticism, will it take you where you want to go? Well, it might, actually, depending on how it is said and how important it is. A random snipe won't get the results you want. It's just more negativity to shovel out. If you say, "THERE YOU GO AGAIN WITH THOSE STUPID QUOTES!!!" ...that probably wouldn't get positive results. If instead you put it, "You know so many quotes, but what i'd really like to know is what you think in your own words." ...that might get a very positive response. So as much as possible, try to think of the results your comments and actions are likely to give.
Start with yourself, and you'll never lose. As YOU step into the behavior and life you'd like your family to become, it will start to happen. If you find some time each day for enjoyment, that will help move things to where you wish to go. If you show love to your husband and all the kids, it will help bring peace and positive things in. Remember to focus on where you wish to go! Each comment, each action you do in any moment can either take you closer or further away from the life you want. Blame and criticism won't take you there. Even focusing too much on the problems won't take you there!!! Why? Because when you focus on the problems, you see the problems, and where you wish to go is not to the land of more problems and blame, but to where you are happy and your family is loving and warm and happy, right? This is sort of an application of the Law of Attraction. Yes, there will be things you need to address with your husband about the issues in your marriage, but if you are to get where you wish to go, it needs to be shifted towards those things that will be in your life when it is the way you wish. Positive communication. Having fun together. Listening. Communicating positively. A truly blended family, where everyone feels together and one, loving and loved.
Do you think these suggestions will help? What do you think? Are you going to try them?
Good luck. And remember your family does love you.