Not disabled, but what you're describing is why I moved out of my grandparent's house when I was 17. I knew my grandfather would never go for any of it and would be rude and condescending. I also worried that he would interfere if I were to do anything towards medical transitioning under his roof.
It was fairly easy for me at the time. I just took out student loans and went to an out of state school. The first year was expensive, but after that I got hired as an RA and housing was free. My boss liked me a lot, so she hired me to stay on as a year round staff person. I never had to go home ever.
Maybe something like that would be a possibility for you? Not sure what your feelings are on higher education.
I think Elis offered a good suggestion. I don't know that YMCA houses anyone here in the US anymore, but it might be worth looking into. I am also in a Facebook group for trans people looking for and offering housing. You could potentially find yourself a roommate or an inexpensive space that would be transition friendly.