New Idea, If whatever your doing now is working, which obviously it is, until he casts ultima,
Ultima requires MP right? His MP is only 999.
Use Mana Springs to knock out his MP, keeping him from being able to use ultima or flare. Do this as soon as possible.
Each Mana Spring takes out about 180, keep doing it until it's down to Zero.
Then just keep doing what your doing, and forget auto-life, and still use your BHPL.
Side Note, I've not successfully done this yet. I did use enough Mana Springs to knock out his MP, but then he killed me.
(I didn't try to use BHPL.)