I understand this might seem like a unique situation to you, but I've been on these boards for eight years and it's far from the first time I've read a story like this one.
He doesn't know who he is going to be on the other side of recovery, if (and that's a big IF) he even gets that far. He is saying he needs to throw every last thing he is got at recovery if he is going to make it work, and make it last. That means even the promise of a potential relationship in the future is too much for him to commit to right now.
Most addicts don't get in to recovery at all and of those that do, very few have the wherewithal to put it before everything else in order to achieve it. He told you it was life or death. Believe him.
Personally, I don't think staying friends right now is good idea for either of you. He has plenty of support from his sponsor and other addicts, and you need time and space to even think about moving past this.
No one can say what the future will hold for him, or for the two of you together. The odds that you have some healing to do from your last relationship with an addict seem pretty high from what you've shared. I know this is an incredibly painful situation but he really is trying to do the right thing for both you. I hope that you will let him.