I have suggested watching it together and he was somewhat receptive. I set it up to make it as easy as possible for him, but in the end he wouldn't do it. We have talked about what it is that he gets from it and it was difficult for him, but he did tell me. I won't give the specifics, but the first thing you listed is pretty close. Actually, the stuff I have found that he watches is pretty vanilla stuff considering all the crap that is out there. It's not soft core by any means, but nothing bizarre or extreme. And over the years, it seems to have been pretty stable...ie not escalating into the more extreme stuff.
One thing we did try that was somewhat successful was doing sensate focus exercises. I wouldn't say that he was enthusiastic but he went along with the program for awhile. We never progressed any farther than just touching, but even that was a pretty big step forward. We were doing it pretty regularly..once a week or so.. then he got sick, then I got sick, then we had house guests, then we were guests at someone else's house and it just stopped. He didn't bring it back up and every time I thought about it, it became less and less appealing. That is kind of what brought me to where I am at now, when I realized that I just didn't care enough anymore to be the one to bring it up and make all the effort to make it happen
That actually sounds very positive given how ugly most things can tend to be!
If your husband was uncomfortable watching porn with you, it is because he feels you will be too harsh and judgmental if he fully allows you into that world.
In the event you want to continue to try somehow... Since his behavior with porn is problematic, you should not enable that pattern of behavior. Instead you may want to find a way to let him know that you care about him and that he should trust you enough to not be ashamed.
Since you know what kind of porn he likes, if you are brave enough you could make a video of yourself doing something solo that you know he would enjoy watching later while he is alone. The purpose of that would be to allow him to experience his sexual ritual (whatever that may be) in privacy, but with the idea of you there in a way that is very present and conveying a message that you want to participate with him in a caring, trusting, and loving way. If you have never done this for him before, it would be an experience of shock and awe for him for which he should be very open to discussing if he was able to appreciate it.
In the event you are not comfortable doing something like that, or fear that such a video may be shared/copied without your permission then don't do it, or talk to your husband first and ask him to help you with that aspect of things if he is interested.
While I know it is difficult to get the motivation to be the one that has to do something to make things happen, you sound like someone that would regret walking away if there was something you could have done to get his attention and help him finally open up to you, and start being closer to you instead of porn.
Perhaps this is a bad idea, but at least it might help give you an extra way to look at things and come up with an even better idea of you own.