Well you hit the nail on the head when you said that porn has warped his mind. Satan knows his subject very well. He doesn't have to work to hard if he can get in through this door.
The first thing I would suggest is that you get a copy of "Power of a Praying Wife" and start praying the chapter on "His Sexuality" daily. You need to attack the enemy. Prayer and God are your only hope where this is concerned. Good news, God specializes rescues.
You have a huge hope, your husband is a Christian, which means that he belongs to God. Yes, he has wandered far, and he has covered himself with sin, but it is far from hopeless.
Do you have one or more Godly women in your life who will join you in prayer over this? Find some, get honest and get praying.
Oh and I'm sure that it goes without saying, but do NOT agree to any sin with him. When he brings stuff up, tell him that it grieves you and the Holy Spirit to hear such talk come from him, a child of God. Remind him ( and yourself) who he is in Christ. Keep your focus there. And when you are weary and weak and at the end, call up a sister in Christ and let her carry you. Lean on God, lean on the body.
"No honey, those shoes are too small."