I am going to respond to your second question first:
I think that it's very important to let him know that you will love and support him.
That means assuring him that despite the emotional turmoil and (natural) judgment you may have as you come to understand his past and current deeds, you will not abandon him. Beyond that I would emphasize the judgment. If you increasingly judge your husband for his behavior while in addiction, and use it to define him in your mind as a X-o-phile (fill in the blank fetish). it is crushing, and can instill resentment.
Just as important as all of that though is to be honest with these emotions with him. You are likely going to feel many ways about him, you will likely go over memories in the past and have to revisit how you feel about them because you may suspect or know that he was masturbating at those times. Be honest with all of that, but do your honest best to love him through that pain. Let him know how what has done and, in the case of relapse, has done to you in that moment has affected you. Don't be afraid to be angry, sad, fearful, and any other emotion that this might bring up. Still all of that should be tempered with love and patience. Do your best to not paint him as a villain, a monster, or broken. You are not perfect, you will almost certainly mess this part up, but it's always ok to come back, apologize, and return to the healing process. He is going to have to learn to do the same.
A very healthy tool to help going about being honest, but also committed is to establish boundaries. If you feel violated because he had been using, then you may want celibacy for a time. It can be extremely healthy that if he relapses you have a set time of celibacy every time. I've known of wives who would have their husbands sleep in a different room for these periods.
And as to you first question,
I think, as mention above, being honest and setting boundaries are huge. Another is that you need other women to talk to. You can talk to your husband about many things about all this, but if you try to process everything with him and him alone, you are going to put more on him than he is able, and not help his recovery. You need a woman to talk to about all of this. The best is if you can find a woman who's been through this. Even more if she stuck through it, and is now still with her recovered husband, but a woman who is currently going through it, or a woman who went through it and left her husband. Being able to describe your experience, thoughts, feelings etc with someone who can empathize can be very cathartic, provide you new perspective, and help you to better navigate those difficult experiences you will need to go through with your husband.
How do you find that? Look for groups dedicated to recovering partners of porn addicts. There are many online, some in church groups, others I think SAA meetings have.
I am only scratching the surface, and I don't have time for a longer post. I am trying to explain concepts and methods I've learned throughout my recovery journey, having had a relationship break apart because of this addiction, but also going through a therapist guided group recovery program with several men that are now over 1 year sober, and had mended their relationship with their wives markedly.
