Hi, Abby.
Saying this gently: there is nothing in your post that tells me your SO is healing.
He is going to go to detox, but hasn’t?
He is going to stop using, but he hasn’t?
He is sorry he has caused you pain, but is distant and uncommunicative.
You are hearing words.
Look to his actions.
When he stops using, when he goes to detox and rehab, when he openly and full heartedly accepts that he is an addict, then perhaps, perhaps his healing can begin.
Meantime, I would treat his words as what they are and look to see if he is acting like someone who truly wants to be clean and sober.
I just don’t see it right now.