So sorry you are dealing with this. It is very difficult, obviously.

Addicts quit when they are done and not a minute before. They don't quit for you or anyone else.

Relapse right out of treatment is a common story. I did it. Lots of people do it. It akes awhile to really get recovery. It takes practice, in my opinion. Repetition. If you want to hang around for him to figure out that he is done, that is just a choice you need to make with eyes open. Not sure what his drug is, but he of course could die. Addiction untreated is not uncommonly a fatal illness, as you know.

You also have to think about how best to care for your own illness. Is the stress of waiting up for him to come home hammered again good for your bipolar? Likely not.

There is no right or wrong way to do this. If he keeps using, eventually, you will leave because everyone has a limit. Everyone. The question is--what is yours?

Love alone is not enough to make a relationship work long-term in our current universe. That has been my experience with multiple women over multiple years. Just my take and YMMV. Sending you support and hugs.