Hi Silverado...I'm just popping in here and I don't know if I can help at all but...there is something kinda glaring at me in your story. Its kind of a red flag, at least from my view of it but maybe there is something else that makes it not so red.
Here are two quotes from your posts above:
"He shows no reaction to visual stimuli, i.e. me in a hot outfit, lingerie, or nothing at all."
"H has always looked at porn, although I can't say he was obsessed with it. But when you are not getting sex in your marriage and you know H looks at porn, it feels like an affair. Especially since he has always been secretive about it."
There is a discrepancy between these two statements. I am a little worried about the porn, especially if he has been overly secretive. What I am getting at is that maybe the porn is something "other" than garden variety? I mean, if he is visually stimulated by porn he should also be visually stimulated by the sight of YOU...in theory at least. I hope you see what I am getting at without me having to say it out loud?
Can you expand on this at all, or do you know any more about this? Have you discussed the porn with him?
I know that when I was married, there would be times when I would masterbate (not with porn but...), somewhat frequently, but I didn't want sex with my husband. In some ways, this was the typical "I am too depressed/tired/whatever to try to pleasure you, but I can do this for myself quick and easy and without you even knowing about it." At the time, I did not see the connection and I didn't feel selfish about it. But now I feel differently.
I realize now that I was "spending" my limited sexual energy that way. If I had not "spent" it in the boring, mundane activity of masterbation, I might have had more of it to direct toward my husband. (In fact, in my current relationship, we have a "no masterbation without permission" rule, and this is mostly for ME so that I will not waste any of my precious sex energy on an unfulfilling rub down and instead, I save it all for sex with him). So my point here is that if he has even a little bit of sexual energy, enough to spend on porn, then he does at least have SOME...and it is selfish of him not to spend that on you!
This is not to say he is mean or selfish in general. These sexual issues are a separate category and many times, we are just dealing with a person's long time habits. They are not meant to hurt any one else but at the same time...if it DOES hurt someone else (ie: their spouse who is going without) then it does need to be addressed.