Have you had the dog for very long? Peeing and refusing treats can be a response to fear. It might just need some time and patience to feel safe and at home.
It sounds like almost the opposite issue from the OP. For this dog, even a harsh word could almost be considered abusive. I'm guessing you aren't happy when the dog pees on you, and any negative response is likely exasperating the issue.
I suspect the fear needs to be resolved before the issue with the steps.
He's a 2 year old Shih Tzu and he's only lived with us (since 3 months old). He's never been mistreated in any way we are always gentle with him. Not even harsh words.
We have no idea where this submissive/timidness comes from. No kids in the house, just wife and me. For some reason, the kitchen where his food dish is located, is scary to him. He will go in to eat/drink, but as soon as he's done, scurries out.
He LOVES treats, but he won't work for them. If you stand at the top of the stairs with a treat, he will just stand there and look at you.
Here's another weird thing: there is an alcove on the front porch with a bench. If you go over and sit on the bench, he will climb the 3 steps, run over and jump up on the bench to sit with you. But otherwise, he won't go up/down the stairs consistently.
If you hold him at the bottom step and put his front paws on the step, he will then go on up the steps. Same thing going down.
This is so strange. We've had four other Shih Tzu's and none of them had this problem with steps. Our other ones even went all the way up and down the basement stairs all the time, no problem.
Other than this bizarre issue, he is a wonderful little dog. Very sweet disposition, loves to play and be close. Is very good with other people (not timid at all). Never has "accidents" in the house (other than the little squirts when you pick him up). Doesn't bark a lot or have any other "bad" habits.