You make some good points but I think your arguments may be biased the other way.
The thing about guys wanting to do what they see in p 0 r n is an exception, not the rule, and when they do in some cases it's positive. Let's say for example some couple only ever do it missionary but the guy says hey let's try some other positions I saw in this video and they try it and end up enjoying it, or bring in a blindfold, or drip candlewax etc. etc. well guess what.. they just enhanced their sex lives. I am turned off by anal sex, though I've seen in p 0 r n, however I know there are lots of women out there who enjoy that. I probably will never do it even though I've seen it in p 0 r n, even if some future SO wanted me to. A guy who tries to inflict a threesome with another woman on his wife if she isn't the one asking for it has bad judgement or is selfish and that's not the fault of p 0 r n, that could be from any of a hundred different reasons including being dropped on his head as a baby. There's no rule for this stuff, it's all a case by case basis.
It's usually single guys who check out p 0 r n, but your requirement of always thinking about the SO seems a bit unrealistic to me and I don't think it's what would be best even if partners could do it. I mean, if I only thought about a SO all day I wouldn't be able to function in life, at work, with friends, go to the bank, refuel the car, that's why being head over heels in love is usually so short lived. I know my SO still turns her head when a guy with a nice butt passes her by on the street. I know she still has dirty thoughts when she sees the ads for Troy. It's fine. I'm glad she has a healthy sex drive. As long as she doesn't act on those feelings towards other guys there's no problem.
The rest of it I mean so many women kid themselves and think they're above men who check out p 0 r n, but there are a hundred other outlets for women (not so visual but more sensual) that serve the same purpose, get em fantasizing about sex, but they fool themselves it's somehow different from p 0 r nography. Soap Operas, Harlequin 'Romance' Novels, Cosmopolitan et. al. They're all equally formulaic as p 0 r n is. A lot of it also has the same element of misandry as some p 0 r n does. "Mistress Claira knew what she wanted from the tall pirate and she was going to take it!" I've read the fashion mags. They are always talking about how to manipulate your boyfriend, how to manipulate your husband, how to get them to do what you want them to. And when women 'dish' with each other half the time it's just a big man bashing session. "my man's such a slob" "oh don't worry Suzy, all men are" A lot of the responses by women to women on this here forum are very misandryous (sp?). And I don't know any guy who has a rubber vagina in his dresser, I've known dozens of women who keep a particular shaped piece of plastic.. I found about these purchasing parties or whatever you call them a few years back, that's not the classiest habit the gentler sex has been known to maintain but it's ok, it doesn't upset me, if it makes your time alone more satisfying for you then more power to you.
So the point I'm trying to make is I know sometimes p 0 r n can be a bad thing for already-stupid guys but if kept in context it can be a good thing and females have equivalent stuff too.