After my husband left rehab (from oxi addiction) he is now attending intensive outpatient care where he's learning what addiction means and how to deal with it. Once a week there is a complimentary group for family members of addicts where we also learn about addiction and how to support them and take care of ourselves at the same time. You should look around and find out if there is such an educational group out there for you. It's been immensely helpful. My husband is also following the mantra of 90 meetings in 90 days. Is your husband going to meetings? If not, he should start. It will give him a place to vent, relate and learn. Remember the 3 Cs: You didn't Cause it, You can't Control it and you can't Cure it. All you can do is take really good care of yourself.
You do sound supportive and honestly, that is all you really can do. He has to want to stop. He has to not want to go back to it once he is clean. Its hard. Its an everyday battle. But, he can do it. He needs aftercare. Its imperitive. He cannot and will not stay clean without it. Even coming on here can be helpful and educational. Maybe therapy or NA. Anything that he can talk about his issues. He may not think he needs it, but when he relapses, he will know why.
I truly with you the best. Keep doing what you are doing to help him. As you said, you can't make these choices for him. You are just there to help and support. It goes a long way when you have someone supporting you, trust me. So many on here hide their addictions from their partners for fear they won't understand. I, myself, am one of them. Well, he found out. But I am clean now.
Good luck!