Nope, you are not crazy at all. It takes time to prove ones self, and she has some proving to do.
I also think that you need to do a couple extra steps in my opinion:
One, since you are going to share legal custody, make sure you put provisions in that should she be unable to make sound decisions for son that it reverts back to you. This protects you and son should she go off the rails in the future.
Also, put provisions in for what happens should she fail the Sober Link monitoring (she fails, it goes back to supervised for X amount of time, etc).
Just my two cents!