Why can't you move back in with your mom? Sounds like living with her can't be as bad as that awful uncle! Shame on your grandparents for not sticking up for you. I lived with my gramma and aunt for a few months when my daughter was a baby and my cousin (the aunt's son) treated me like your uncle, but my gramma laid into him and told him I have as much a right to live there as he does and as long as she's alive its her house and she'll have whomever she wants living there. I loved my gramma. She ruled!!
Anyhow...you should check into moving back in with mom. I'm weird and annoying, too, and that's no reason to for people to be rude and hurtful. Heck, look at my son's picture in my avatar!! Its obviously hereditary!!

I don't care how old you are, get the heck outta there!! You deserve much better!