This was me almost exactly. I learned a couple keys things before getting myself out of the situation.
1) He is going to need a care taker his family saw me as a way to take the pressure of caring for him off their hands, they knew he can't function independently.
2) he is isolating you, gaslighting you, and manipulating you. If he closes your entire life off no one can question his instability and he is more likely to be able to pass instability as Love. It's not, I get it though at the very end before I left I wasn't allowed outside at night (I still can't believe I allowed that) isolation is a powerful tool for manipulation.