I don't think he'll ever be completely gay. He says he doesn't have the urge to fuck another man or be fucked by one. His "gayness" seems to revolve entirely around his childhood experiences: him sucking his stepdad's cock.
I might puchase a viagra or cialis and see what happens...
He can say that now... and I am certain he means it... but as with normal sexual contact... as the cocksucking becomes something far more common and less intellectually novel... he may be driven to more extreme sensations... he might not... but a lot might hinge on your reaction to it... If seeing him suck another man creeps you out... that is a tempering effect...
His expression of never wanting to get fucked by a guy may in part be due to subtle cues you send about how you feel about the idea...
...however, if you developed an ability to enjoy seeing him service another man ( which would probably be necessary for you to really feel good about the 3-way situation long term) then he would begin to feel safer about further experimentation.
I think a full time third partner would certainly have to be either someone Bi... or someone willing to dominate your S/O via the blowjob thing... There are men out there who have no problem screwing a guy and still feeling straight.
But it would, ideally, have to be someone you both felt affection and closeness to.
The pitfall is that this might well backfire... He may well be unable to deal with your having actual feelings for another man...
Its something to discuss with him in any case...
In the only couple I have ever known make this work the wife turned out to be turned on by seeing her husband take it from another man.
She had sex with the both of them, or either of them, only twice a week. But her husband was servicing the other guy daily.
But the guy came about as a man her husband had the initial relationship with..
that is, she didn't bring him into the relationship, he did. But it turned out to be a guy she really could click with.
Her husband's prior connection to the guy made the jealousy issue moot.
If you have a problem with his homosexual side that you don't feel you can get around... then it may be time to start circulating your resume... that is... looking for more than just another guy to please you husbands need... but looking for a replacement guy.
As to the drugs.... some men do not respond to one or the other... so if you donlt get a good response with viagra, try the cialis, or levitra.
I can tell you from my own experience that cialis makes me feel like I am 30 again, in terms of how I respond to sexual cues... doesn't spring a permanent boner... just makes things stir, and stay stirred, more the way they used to...
But its important to note.... its not usually an issue of lack of interest... its the biology of Nitrous oxide and how it affects the nervous system.
Women should know that what may seem like inattentiveness, or a lack of passion is often simply the man trying to avoid sexual situations for fear of poor performance.
Its not psychological, not anxiety... its a leaky hose that doesn't hold pressure like when it was new, no matter how much you want it to.
If that is part of his problem... then the blue pill may be revolutionary to your relationship.
If he can respond the way he wishes he could, without the extra-intense stimulation of forbidden ground... then this fetish of his may abate and become less prominent.