Main content REDACTED to avoid this coming back to haunt me.
Original post described a co-founder who did not listen well (esp. when he initially disagrees or is at fault), had a big ego, dismissed my concerns, and was not a fun developer to share a codebase with.
When you lose a founder, you lose the motivation and confidence to continue, you lose part of your vision, and the other half of the "brain" in your startup. The key to a successful startup is to first have a strong relationship and chemistry between the co-founders. Second, is to have a good product.
So if you're miserable, find something else to make you happy. Just beware that many of the most brilliant technical people are going to have their own "tics" ... perhaps a set of closed-back headphones would help?
Finally, you should also ask yourself what he might be thinking about you ... it's a valid question. After this divorce happens (you've already decided), think about the traits that will make a good marriage next time.
Other than that though it just sounds like you two just shouldn't be working together. If I didn't enjoy beings around my co-founder(s) it would ruin the whole startup experience for me, I just wouldn't do it.
You could 1) accept it and endure it (but your company suffers because of it once it goes public or is more public) 2) confront him about it because this is a 'company issue' and you have to resolve it if you are going to move forward for the good of the company 3) cut your losses and start anew with a new cofounder or a new startup (4-5 months into it shouldn't be too high a price to pay for more headaches later)
From your point of view (and I've haven't seen his side of the story) you have made reasonable concessions, and any more concessions on your part I don't think (from reading your post) will unlikely resolve things.
Good luck.
Another important note is that you need not like the person you work with. Think about it, what are you working for? I hope your answer is money, if not then please ignore this. If you think about it, money has no feelings. As should you. This by no means, means going and robbing a bank or anything that extreme, but it does mean business should involve no emotions, while at the same time be ethical.
I said that if I was going to be busting my butt for the next few months or years, I'd want someone that I would really enjoy working with and can get along with and that's mellow/laid back/low key/no drama. His talents and skills were lower on the priority list than that #1 must -have.
I hope you have better luck finding someone that's no only skilled but that you can get along with and is compatible with you work-wise/personality wise.
Also try to show as much loyalty as you can to the person that you hired, as they're apparently someone competent who was caught in the crossfire. Perhaps you can fit them in if you happen to start something new soon. Heck, maybe even that person would be a better co-founder for a new venture.
Hang out with them in a social setting. Hire them to do some minor work for you. Do whatever you have to, to find out what they're REALLY like before you make it official.
Now that you know it's a bad fit, figure out how to move on.
Patch things over for the sake of your baby, end things amicably, or take your baby and run baby run.