> You really should be talking face-to-face as much as possible and I do not understand why you are sending e-mails in the first place. It sounds like you two live and work far away from each other and in that case I believe you are doomed anyhow.
This is the biggest red flag I saw. You guys should be talking voice or meeting face-to-face more often. You will not solve personality issues via email that neither of you have a lot of time to spare for.
If the OP doesn't make at least a serious attempt to re-connect with his founder then he's at least half of the problem here.
Make time to work with your cofounder vocally, in-person if possible. It's too easy to dismiss concerns via email.
He's counting on you and you both have to put up with a lot. If you can make it through this by stepping back and realizing that it takes two to communicate, then the business has a chance. You might have to try harder to communicate with him but can you honestly say you've tried your absolute best to make it work? Are you going to let communication breakdown without trying as hard as you can to fix it?
Things will get harder as you go on-- this kind of a problem isn't a great sign either way, but if you don't try your hardest the bad sign may very well be about you. Be absolutely convinced you did everything in your power to compensate for his weaknesses (and yours).
If your heart isn't in it enough to try your damnedest, then perhaps that's the problem and not the communication issue. I'd still try to address that because it doesn't sound like it can get much worse if you're considering leaving.