This!! This is everything I thought when I read your post.
Please take the time to focus on you and know your self worth. I have been there, worrying about whether he was cheating. I feel like that was my way of coping with my feelings - it didn’t work it sent me more crazy!! But looking back, I think the worry of him cheating was my gut instinct trying to convince me to walk away. Would I have walked away if he had cheated? Yes! So I focused on that so I could escape without the manipulation. That’s just my story, yours may be different but I couldn’t pass by without sharing it.

As for him being in rehab. Leave him to get on with it. If he wants to get better he will, if he doesn’t he won’t. If he’s going to cheat he will do it wherever he is. But like HCD said, you have bigger things to worry about. You need to be worrying about you!! Treat his time in rehab as your time to rehabilitate yourself.

Good luck!