Your predicament is not an easy one, and I respect very much your initiative to ask for advice on this touchy problem. In addition to complimenting his honesty and tfila as you mentioned, I recommend that you discuss the following points with your boyfriend:
The biggest tikkunim or challenges facing our generation, right before the geula (in addition obviously to Eretz Yisrael), are tikun hamila (to elevate the spoken word- Lashon HaRah) and tikun hamila (brit hamila- the exaggerated sex drive). The internet has extremely exacerbated both problems, and I unfortunately know rabbis who have dealt firsthand with cases where pornography has even ruined marriages. These are the challenges of our generation.
The Rambam (Guide for the Perplexed 3, 41) explains that the Torah threatens the most serious punishments where there is a special need to deter, as in the following cases:
a. The seriousness of the transgression.
b. The extent of the frequency of the problem.
c. The extent of daring (people dare and therefore need to be deterred), for example, if the transgression is done in private.
d. The easiness or accessibility of the transgression.
R. Elisha Aviner once pointed out, that pornography on the internet ironically applies to all 4 (!) of the above problems! The seriousness of “lo taturu acharei… eineichem”, is recited twice a day in Kri’at Shma, because sexual day-dreaming is an all-encompassing problem which can get someone totally off-track from concentrating on life. The frequency of the problem is well-known to anyone who has the problem, more than anyone else. The accessibility that porn today is only a couple clicks away, and the fact that it can and is done easily in private, without too much daring involved, would explain why the Rambam and others deal so severely with the mitzvah of “shmirat einayim”.
Make him aware that the Rambam explicitly lists someone who looks at pornography as one of the 24 cases where tshuva is particularly difficult because many excuse themselves saying, “I haven’t done a forbidden action- I’m just looking”, without realizing that looking at such sights is a forbidden action in unto itself, and is super-easy and common, etc. (Hil. Tshuva 4, 4). As soon as he realizes the severity of the action, that’s an important start.
As far as you are concerned, pornography is not just a religious problem like if he doesn’t keep kosher or wear a kipa, but it unfortunately conveys what may be your boyfriend’s relationship, to a certain extent, to women in general. From marriage counseling experience, I would definitely be wary of entering a relationship with someone who can (and does!) see women as objects and sex symbols, to be used for personal pleasure, while missing the beautiful intimate mutual gratification which are basic to every loving healthy marriage.
I suggest discussing this with him, in addition to pointing out from the start that “I, or no woman, wants to have to compete with porn stars, and be continuously compared with them and what they do, either consciously or subconsciously, either aloud or secretly.” If that is their “profession”, and those are his expectations from his wife, it is definitely going to be difficult to live up to such hopes or fantasies. Pornography is an easy “virtual” way for men to “get their kicks”, and actually distracts them from investing the effort to build a healthy, normal relationship with a real, live woman, answering to her needs, working towards mutual love and satisfaction, etc. He must stop viewing women as sex objects. Simply put: real love for a real woman, and cheap pornographic lust for a different woman’s body, are diametrically opposed!
I would also suggest giving him some positive incentive. Tell him that you are interested in marrying a real “man”, someone who has the g’vura, the “guts” and strength to overcome even this strongest of drives!
Regarding discussing the issue together, the Or HaChaim HaKadosh (Vayikra 18, 3) writes that one of the ways of the yetzer hara is to get you to talk about the problem of the yetzer as much as possible (why do teenagers like to talk so much about negiah?!). The logic is obvious, and accordingly, it’s best for boyfriends and girlfriends to talk about pornography or even negiah, as little as possible, for sure not a detailed day-by -day account. On the other hand, it’s obviously important for you to know the answer to that black and white question: if he succeeds in overcoming this weakness, or if he continues.
This is his battle, and there really isn’t much that others can or need to do. Pornography is a terrible habit, but it can be broken immediately, and is not at all like drugs where addiction is physiological. He can, and should say that he is stopping today (not even tomorrow), if not for his sake, than for your sake. To put in Rimon, Net-tzach or another pornography filter immediately, simply takes one phone call or email. On the other hand, he should try and get involved in positive, active pursuits to which he can and should direct his energies, learning Torah, volunteering, and l’havdil, active sports, etc.
To be supportive is always good and helpful, but to be supportive as a girlfriend regarding an issue which comes at your expense is difficult, unfair, and probably even unwise to ask. If pornography has ruined marriages, why get involved knowingly in such a relationship?
Again, real love and cheap pornography are diametrically opposed, and it would be wise, worthwhile and much more pleasurable (!) for him to invest in a real, idealistic long-term relationship of love, rather than cheap, “virtual” illusions and fantasies. As soon as this is clarified to him, his decision shouldn’t be difficult.
Please let me know if I can be of further help, and even better, please let me know if he succeeded and that you are building a Bayit Ne’eman b’Yisrael!! B’hatzlacha!