I think you are doing the right things the right way. Even though he is an adult, shaming is the wrong thing and counter productive. [The same holds true to alcoholism for example.]
Understanding, compassion, with concern, goes a long way. So does positive support, but with expectations. We are visual, and if we have been hooked for years, it is very difficult, but most certainly NOT impossible to improve. You understand and forgive, but time to put on your big boy pants.
Even after progress, expect a rare fall now and then, but as long as your husband tows the line the vast majority of the time your BOTH doing well. It is a life long struggle for most of us, but I must say, it has to be easier for married.
Kudos to you for not confronting him during the act. Shame like that is really difficult to overcome in a relationship.