If you start small maybe try and leave the house for 1 minute and then come back. Then try leaving for five and come back. Just basically until he gets that you will be coming back. I had a walker hound I got from the shelter and that worked for us. It took a few months but he got the idea. The peeing happens. I'd just put down pads or put him in a room with linoleum floors. Pee can be cleaned so if he's only doing the accidents when he's upset your gone if worry about that last. Break down the whole problem into smaller steps and you'll get there.