Leave, and don't look back.
At this point in life fella you are either going to have to plough it alone, or forever be stuck. It will be hard, the car may well have to go, but you will be a happier and stronger person for it. I think I said that I could see this happening at some point when it first kicked off, and I take no delight in being right this time (which is very unlike me!).
Living with people who bring you down is never going to work long term, and I'd rather be happy and broke than sad and comfortable.