You saying
. . . but it literally hurts to live this life without him
is a big red flag you should pay attention to for you. You also need recovery and healing from the relationship so you can take care of your boundaries and make safe and positive decisions for your future relationships and life.
If you've been in a kind of "holding pattern" since he left, well, I would suggest that you are not yet in recovery and very vulnerable to getting back into a relationship prematurely that isn't in your best interest right now.
Him saying
. . .he believes having me in his life again will be another inspiration to keep him on his better path
is a red flag coming from him. He is in charge of his recovery, and being an "inspiration" is sort of like being a resource where he isn't relying on himself, but someone else to prop him up. If so, he will not be successful in the long term.
Two dependent people don't make a stable couple. You need to be strong and happy in your own company before you get involved with anyone, let alone a recovering addict who has already ghosted you recently. That shows he lacks empathy and maturity. Healthy adults don't do things like that to people at all, especially ones they have known for fifteen years. Not cool and a bad sign.
Right now he is one tiny six-month step away from the open door of addiction. He needs to focus on recovery, not a relationship in the near future. That's a distraction from the hard work of recovery. When someone has been addicted from a young age, they have a lot of growing up to do, and it isn't easy. The ghosting incident suggests he is very immature at this stage.
Be careful and take care of you. It seems like you've been on the receiving end of a whole lot of hurt from this person, and no amount of love or time you have known him excuses that--