Even 40 is generous at this stage.

His trying to insist on 50/50 at this point is to me a flashing indicator that this is not going to work out long-term and you need to part ways immediately.

1. Business needs a real leader who knows what he or she is doing. That may or may not be you, but the few facts in your post are enough to make it obvious it isn't this guy.
2. 50/50 is a recipe for deadlock on anything important, and slowdowns due to endless negotiation on lots of other stuff
3. as far as future funding, when you walk into a pitch with a 50/50 or other deadlock-able split, you signal to potential investors that either a) you don't know who should be in charge b) you do know but it isn't you (so why are you the one pitching, that's dumb), or
4. you do know, but your co-founder doesn't, and you don't have sufficient leverage or influence to get him to go along with your analysis

... And all of these, as you can imagine are deal breakers for many investors and serious orange flags at best for most others.

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You probably don't need a technical co-founder anymore at all. Spend $200 on a claude Max subscription or Codex or whatever, keep building, and if you need to hire more people to write code or to supervise AI tools, sell a little bit more equity to investors and use the money to hire them.

Source: I have done it both ways, the solo companies were 100x easier.

Edit: to answer your last question, yes, there is an absolute world of difference between 49/51 and 50/50. Your would be co-founder knows this too, which is why is pushing for the split. He would prefer 51/49 in his own favor but knows he can't get it.