Reddit mentions of KOOLTAIL Washable Pee Pads for Dogs - Waterproof Dog Mat Non-Slip 2 Pack 36" x 41" Whelphing Pad Puppy Training Pad for Dog Playpen

Here are some more comments (I've worked in animal rescue and zoos).

First, you've tried way too many things in just 4 months and now you're about to try some more stuff. Whatever you do, at least stick with what you decide for at least a coupe of weeks. (I'm assuming the pup was about 2 months when you got him).

You have now entered into the classic "intermittent reinforcement is the strongest" territory. While straightforward operant conditioning works (where you always reward a certain behavior), intermittent reinforcement is the strongest (whatever works as positive reinforcement is only given occasionally - this locks in a behavior strong than operant conditioning).

And, you're convinced that "nothing works" even though you did intermittent conditioning AND you didn't stick with any one thing for very long. Now, you're about to change several things at once (again). If Dog likes even one of those things, Dog will continue thinking he's getting reinforced for doing what he's doing.

I'd start with getting a mesh style crate and putting a tarp under it on the floor. On top of the tarp, put several of those washable "puppy pads" (not the paper kind) and put the crate on top of that. If the puppy can still get to the pads to chew on them, get a crate with smaller mesh on the bottom.

The goal would be that even if he does pee in his crate, the pee will not be on his body. Do not put bedding in the crate at first. Then, get used to changing out those pads each day. You will have solved one of your own major problems (having to wash him all the time). You will also, hopefully - after a month or two - gotten him used to not being in his own pee.

My concern is that you now have a very confused, depressed pup. You seem to think you know what size crate is best when in fact, no crate has solved the problem. Bigger is always better for a situation like this. That's why most animal shelters have big ole concrete kennel runs. It is really unusual for a dog to be in a space where they can only turn around and lie down.

Frankly, nearly all animals placed in small cages/crates like this develop behavioral problems. I used to teach and do research at a large animal shelter and it was clear that dogs with various problems did better when in a large space. Get the largest crate you can accommodate. Make sure it has a mesh bottom.

Do not use one of those portable plastic kennels! Use a proper crate.

The behaviorist is on the right track. If I were you, I'd take several days off work and re-start with basic puppy training. Puppy goes outside immediately upon awaking from any nap, plus every hour on the hour that the puppy is awake. Reward with treat, praise, dancing, etc each time puppy pees outside.

But most important, quit changing things up. It's very concerning that he got urine scald (don't ever let that happen again!) but you can definitely fix the situation so that it's impossible for him to actually lie in urine. He may not like the mesh under his feet at first, but that's a small price to pay for him being clean.

The pads I'm mentioning should have moisture wicking ability, like these.

The pup is getting very excited over the noon walk and that adrenalin is leading to more pee. This may not solve itself until the pup is older.

You've got yourself a set of dilemmas complicated by the lack of backyard and the size of dog. But please, please quit focusing on the fact that a puppy is peeing (that's what they do) and solve the part about him lying in it (that's not normal dog behavior and I'm afraid your dog will need lots of help in getting back to normal).