I think I really ought to chime in here, as one who thinks that, as Robert-I said, God blesses gay marriages and so should we (the church).

I think that your initial feeling of not wanting to jeopardize your existing relationship is right. I wouldn't risk that myself. But, if he's attracted to you too, well, that's a different story. I'd not "start" anything yourself, with one slight exception:

Does he know you're gay? Not that you're specifically attracted to him, but that you like guys in general? If not, that might be an important thing for him to know. And that coming out could also help him if he happens to also be gay or bi.

I wouldn't worry about "controlling yourself". After all, you really do value the existing relationship, and real love will control your lust with surprising ease if you choose to recall it.

Just remember to act for his greatest good, and pray for the grace to see and know what that is.

God Bless both of you, and may this time be a positive, growing time for you both.

In Christ,
~CSL