Depression Support Group
Depression is a real and debilitating condition that is often misunderstood by family and friends. Its meaning can range from a prolonged period of sadness to an actual mental illness with specific symptoms. Find and share experiences with others who are going through the same struggles.

"He has alienated my whole family so I have no one to talk too."
At a time when it is safe, call a candidate within this family and tell them you have been and are afraid of BF and you want to leave, but are too scared. Hopefully they will realize the problem they have is with him .... not you. Arrange a time for them to pick you up .... and give you shelter. If/when BF shows up, call the police. You may even be able to get a restraining order. As for retrieving your property, the police will probably escort you back to get your things. You may have to abandon the car if there is no one to help you get it back.
The only hitch is if no one in your family will do that much for you. In that case, the police are your only protection. The police will have to help you get out ... and then what? You are very much in a crisis situation ...... one that MAY somehow be illegal on his part. Can't prevent an adult from leaving .... not in this country. I think your problem is not so much in leaving but what you will do if you do leave. Hopefully, there will be more suggestions in other replies. Good luck to you.
I have no direct experience with this so I could be very wrong on this, I too hope someone with experience will chime in with suggestions.