since you've known each other for 15 years, i really don't see any RUSH here? you don't have to decide anything today.
six months is very very young fragile recovery. it is and should be his focus. because without recovery, it's back to the drugs and all the misery. starting up a relationship is a distraction that is really unnecessary at this point.
give time time. if he starts pressuring you, that's a red flag.