The trust issues are HIS to repair. Make sure to keep that in mind. Right now you do not trust him and that is for good reason. When you talk to him, be clear that you do not trust him and let him know why you do not. Tell him it is up to HIM to prove himself trustworthy again and that will take time and consistency on his part. Sometimes people are good for a couple months and then they think everything should be ok. That's the not the case. If he is serious and cares about you, he will do whatever he has to do for as long as you need him to in order to gain your trust back. He should WANT to do that. After all, the changes are going to make him a better person as it is.

You don't have to let him back in your life all at once right away. Again, point to the trust issues and maybe just try being together for a limited time at first and let that time grow as you feel he is making real changes.

For your part, you have to exercise patience and understand it is never easy to make big changes in your life. He is going to struggle and may have minor relapses but just make sure to call him on it when you see it. Work on your communication with each other and try to find a way to talk that is productive and solution-oriented rather than argumentative. Talk to each other ahead of time about how you will do this when you have heated disagreements. Don't talk in the heat of emotion because that rarely helps. Walk away, cool down and then talk with the goal of solving whatever problems come up.

Hope this helps.