Normal
You definitley don't want to say anything that he can turn into you telling him he can't do something. I think it sounds pretty good, but I would just say I'm not sure what effect your past will have on what you want to do in the future, but when you get out and have enough time behind you that you have remained clean and sober, you should look into it. This way it sounds like you are encouraging him to look into his dream and you aren't saying he can't do it, but your not sure what effect his past will have on it. Then I would him that you love him and your glad he's looking at positive things for his future.