i wouldn't worry about the potty thing. If he's not ready then I would leave it a few weeks or even more.
Not all kids are dry early - despite what some parents say!
All children are different. If someone has managed to get their child clean and dry at a young age, then they are very lucky! My daughter was two and a half, but both my boys were well over three. Summer is a good time as he won't catch cold, and your only changing little shorts - not heavy jeans, socks, shoes!
I understand you are having a crappy time at the minute - but it will get better.
As for his speech therapy, could you just treat it as going for a nice visit to see ______ - whatever her name is? If it does some good then that's great, and it certainly won't hurt him.
I have known children with quite severe speech problems when they came to me at nursery, and I see them now, in "big school" chattering away!
I agree with the other posts - get some time for yourself. Even a bit of window shopping or a swim at adults only times; a cheapy cinema trip or free hairdo at a student hairdressers might help.
hope the sun comes out soon! xxx