Bubbles
My niece lived with my husband and I and I did not know she was a meth addict. I lived for 1-1/2 years with insanity before I found out. During that time I had her to doctors, psychiatrists, etc. In the end we found a meth pipe in her room.
All I can offer is that if I ever found myself in a similar situation (someone's behavior is bizzarre and I don't know the cause), I would set boundaries. For me that would be, get help or get out.
Adults are responsible for thier behavior and whether it's mental illness, physical illness or drugs, adults living together (married or not) have the duty to live in a way that does not create an unstable, untenable situation for the other.
I have a brother with schizoprenia, a sister who is bipolar and many with depression. They all manage thier illnesses in partnership with their doctor and medication. They live with others peacefully and are open about thier diagnosis and medications. My meth-addicted niece, however, refused to see a doctor and was very secretive when she did finally go (wonder why?).
So, all I can say is that illness or addiction, adults are still responsible to manage thier own life. There is help if they want it and if they don't want it, no amount of "help" will matter.
Apologies if any of this sounded too harsh. God Bless! Prayers that you find a way to end the madness.