I went through this with my husband about 8 months ago when he came home from rehab. I felt anxiety also as he had been there for three months.
While my husband was in rehab, they provided me with a therapist to work with. Sounds like you have insurance, so I would keep this in mind. For me it was great to have someone to help me sort out all those past feelings of hurt, anger. And also to learn how to forgive, focus on the future. We can end up with a lot of trauma depending on what happened during that time of addiction.
Since your husband has been working an outpatient program - then I'm wondering if they might have some type of counseling or therapy for family? Sometimes it's even included as part of the outpatient program.
Don't panic about his coming home. just try to take things one step at a time. When he was active using how could you tell? Behavior probably. So I suggest you watch his behavior. Not every little thing he does, but over time. A few days, a week, etc. I've found behavior and a persons attitude are good indicators of how things are going.
Also, for me... Communication with my husband was very important. We talked about it being awkward, about it being like when we first got married and were living together. We just took things slowly, and in time as he grew stronger in his recovery, got back into to work, and I stayed with my schedule- we found routines just like before.
Also, my husband and I did marriage counseling. We started that when he was early in recovery, about 6 weeks. So depending on your issues, that might also be something to consider at some point.
I think your nerves are normal, but he will have them also. And remember that whatever comes up, to lead a normal, healthy life again he has to learn to cope with his environment and the people in it. He has support now with outpatient, so if he gets stressed or whatever they will be able to help him work through it, until he is strong enough to tackle it all on his own.
Good luck to both of you