Is he crate-trained? He should be! It will help a lot with him sleeping through the night, and taking naps safely and without waking up and peeing right away.

It sounds like you need to tether! Keep him on a leash next to you at all times. Play with him, give him chewies, and do short training sessions as you would do normally. This will also help him get used to being leashed. Make sure you take him outside often! My recommendation is to start with every 30 minutes. It can seem like overkill, but you need to do everything you can to prevent accidents and encourage going outside. Take him outside 30 minutes-1 hour after drinking and eating. Make sure you exercise him off-leash in your backyard often. He should never be without supervision at this age... never. I know it's difficult, but it will get better after he has learned outside is the only place to go potty.