Your post makes me very, very sad.
I'm no Pro, but from what I know a dog does have feelings, but it does not have the ability to plot & be vindictive.
I do know that an animal may use the bathroom out of fear, just as he did when she hit him. The same could go for urinating, if your mom hates him, as it seems, that poor pup knows it & probably fears the next blow.
Had he been completely potty trained prior to this? I believe a UTI can cause frequent & even uncontrolled urination.
Hopefully you can get some more answers here & help for your pup in one way or another. I'll definitely be praying for him.