Well, we spoke at length about it last night I'm going to give him a final chance. I've accepted the responsibility that if he is lying or does mess it up agsin that it'll be my fault for being naive.
I've made it clear that I won't even hesitate to finish it next time and that he needs to earn my trust again now.
We talked about his recovery plan and I was upset to learn he's been doing it alone, other than occasionally talking on SR. I've made him promise he'll get some other sort of support and I'm going to make sure he follows through.
I know this could all still go badly, but as exhausted as I am, I'm not ready to give in. I know I need to take care of myself too, so I'm going to look at any support groups etc that I could join. Thank you all so much for replying, it's been a dark few days and knowing there are others who understand and care has helped so much x