>>29826
I would say the peeing everywhere is an assertion issue. (Yes, I am a dog person)
Dogs don't want to misbehave, they are proud to be in the pack.
You have to let them know what is expected and what is not. A pinch on the back of the neck / slap on the bottom and a stern tone.
I prefer to teach with positive reinforcement rather than negative, and most of my training is positive, but it can't all be that way.
The dog is thinking it is aiding the pack by spreading its scent everywhere -- that is because it thinks you need help being Alpha because you haven't expressed otherwise.
As the pack leader, you need to be the alpha. That doesn't mean being mean, dogs don't think that way. Remember: they want to be the best member of the pack, you just have to take the reigns and let them know how.
You provide the food -- you are the apex predator. There is nothing more to it than that, you just have to assert it.

It may be too late to fix that training now.
If you plan to stay at a friend's house, maybe you can block off an area for the dog? Or put the dog in a tent in the yard (if applicable)? Or a dog run (an outside cage, or a leash attached to an overhead line)?
You can certainly try to re-train in short order, but a new environment may make that more difficult.
I don't want to sound like I'm bragging, I'm not. I've had dogs poorly trained, and then I learned how to do better. It's all about learning to communicate with them, you need to establish signals ("yes/good" and "no/bad" as most basic).
It makes sense that he is trying to take over the alpha position when you are not there, and mark the territory. Again, he thinks he's doing the right thing. You need to assert that you are always the alpha, present or not. This probably involves showing him the pee in your absence, and giving a clear "No." in relation.

I don't want to give out too much personal information, but I have lived on the streets with my dogs. The first two days were rough, and after that... it was a whole new sense of freedom. The hardest part about "getting back on my feet" as far as job and money was in giving up that freedom...
Like I said, what is going to happen is going to happen. You can't change the past, and you can't change the future (yet), you only live in the present.