He has a vision. He wants you to trust and follow. You know he's going to fail. Get out so you can both have a chance to get where you want to go. If he fails, at least you won't be the person who held him back from fulfilling his vision.
THIS.
Apart from that, I see TWO FOLKS BOTH with their own visions.
Unfortunately, these visions do just not go together; this much I can see from your correspondence.
What I will have to grant to that other guy is that he clearly states what he wants. OP, if I were in your situation, I'd do the very same: Put my cards (wishes) on the table, and fight for them. Then, you will both see if your relationship has what I take to be a prerequisite of any REALLY good band:
Whether you can fight hard about what's best to do next, AND whether you can come to a mutually agreeable solution!
Best wishes!
PS: it's just me, but if I ever found out I was abused as a "crutch" for anyone, until they find "something better" (as has been suggested), I'd become REALLY MAD at them: That is unsincere & dishonest - unless clearly communicated by them, which of course would make me leave that relationship immediately!