The one thing I do agree with; is I think the marriage laws should be nationwide.
I have to disagree with this from a States' Rights perspective. The Constitution specifically states that all rights not granted to the federal government therein are reserved for the states to decide.
Surely, 50 states can figure out better than 1 governing body how to work out various problems that arise in communities. 50 states makes a broader base for human problem solving than 1 can.
Lastly, most states have recognition laws whereby they don't undo what other states have done to regulate commerce, etc. A marriage is not invalid just because you step over a boundary. It may not work for state taxes, but your fed taxes would be the same, and virtually all companies now already recognize significant others for purposes of beneficiary status.