We have a 20 year old son that we had to use tough love on after five years on and off of drug abuse and not respecting our home, being lazy, not thriving. My son also has anxiety and depression which is another factor but from what you've said you need to make rules that he either follow or he cannot live in your home.
That sounded harsh to me at first (now looking back I'm not sure why) but it's the only thing that has helped us and helped him. We had to present a united front (his dad and I). They try to play one against the other and especially with a step parent. It sounds like you are a very caring person.
The people on this forum will give you great advice.
Good luck.
