WH here. Porn was a big issue for me, too, and I stongly believe that it led me down the slippery slope to my A. I'm just about 2 years out, and I haven't looked at porn -- or masturbated -- since DDay (my choice).
It's easy to say that porn is the "guy thing," and I used to believe that, too. I also believed that it was acceptable to watch with the spouse. I no longer believe that, for 2 reasons (not because of my A):
1) it took my sexual focus and energy away from my spouse, even when we were watching it together, and
2) it inhibited my empathetic growth.
Once I realied that these other women that I was looking at -- and jerking off to -- were actually REAL women, and were daughters, sisters, mothers, girlfriends, and wives, it made it much easier to quit.
I lacked empathy for much of my adult life, and porn is a major reason why.
BW22, there was no porn agreed upon for your R, and that's that. Even breaking that "a little bit" means that porn is more importantto your WH than you are, or your R is. That's it. I hope he gets it, and if this is a true addiction, he is willing to get help.
Hang in there! It's not your fault, and it's perfectly acceptable to ask him to completely, and totally, stop.