I also don't know why this is anonymous, I don't think anyone would judge you for this... we all have problems, and you're doing your best.

Gonzo gets walks/runs in the early morning or at/after sunset, when it's cool. It isn't even healthy for dogs to walk on concrete when it's hot, so don't feel guilty about that. You can still walk them when it's cool, play with them in the yard, etc, without having to run around in the heat.

I'm also a teenager, and I take primary responsibility for my dogs. It can definitely be challenging sometimes, but my Mom knows about as much as I do about what to do with the dogs while I'm gone, because she knows what I do with them and I've taught her. About the AC, you should get a regular floor fan. They're really cheap and they help cool your room a lot!