That's a tough one. I think you're probably doing the right thing by leaving, but I think more good could come from sharing your grievances with the engineering

That's a tough one. I think you're probably doing the right thing by leaving, but I think more good could come from sharing your grievances with the engineering lead when you leave rather than the founder. If he has gone from being an engineer to managing with no prior experience, it could be he is struggling with learning how to properly manage a team. Basically what I'm getting at is give the guy a chance before you go scorched-earth and try to ruin him. From what you've said it seems like he is willing to listen, and you gain nothing if you're severing your relationship with the company anyways.