I read up through about page 8, and then skipped to the last. It seems to me you might possibly be a bit too focused on the excuse he gave you (religion). He didn't give you a need of his you weren't meeting or which wouldn't be met by polyamory - he gave you an evaluation of a belief system, one you're already familiar with. Learning all the opposing views to that belief system, IMO will ill-equip you. The more you know about it (and focus on it), the more tempted you're going to be to argue and defend against it - which is all the more likely to arouse defensiveness in him. He's not very likely to feel compassionate about your needs if he's busy defending his own.
So what to do? I can't tell you exactly. I'm in a similar predicament. I'm not "polyamorous" exactly. Someone told me on a forum by what I described I was "polysexual". Basically I desire FWB-type sexual relationships with women other than my spouse. I love the different reactions and emotions that come from experiences with different people. I don't desire committed-type relationships such as what I think most would think about in polyamory. Why? I don't have any need to "come out", and I feel completely adequate with these types of relationships. I get to keep all my family close, and I even go to church. No one knows. My perfect situation would be one in which I could have lunch, go to a game, go to a party with a FWB - and yet maintain a close primary relationship with my spouse which meets her needs and mine. With my other partners: No living together, no paying bills together, just time management and a little sharing. I'm totally willing to give my spouse the same. I'm not closed to that changing, but it's a start.
In my personal situation, we have been swingers. But we have always (with the exception of a fairly recent situation) always played in the same room. I'm comparing my desire to have the freedom to play separately from her with some of our friends to your desire to be poly. It's not the same at all - but I listened to the excuses she gave me, as it appears you have, and I tried my damnedest to understand them and refute them; all to no avail. There seems to be some sort of fear there, some need for security - nonetheless I get an emphatic "NO" and then usually a guilt trip and pouting spree to top it off, and I slither back downstairs to my computer room to log back on to forums like this one and attempt to connect with people who have empathy with my feelings - a need she's been unable to meet. There's MANY more layers to this story, I'd be happy to tell. If you like, just PM me. Nonetheless, in order to not threadjack your thread I'll get to my point:
Many times (according to nonviolent communication - ALL the time) the judgments people make of you are in response to some need of theirs not being met. Maybe he does have a belief system that he's relying on to meet a particular need of his (and thus is blocking your particular need?) - but rather than arguing with it - I think the point to focus on with him is how that belief system ISN'T meeting your needs and then describing the emotions you FEEL in relationship to that need not being met. Until he grasps what your needs are and how you feel enough to just have EMPATHY for you - all your "requests" are likely or probable to sound like "demands" to him. Demands require a "one way or the other response" and typically he'll go with the opposite response you desire. This is just my opinion and assessment.
I HIGHLY recommend reading
Non-Violent Communication. I liked it so much I read it twice! lol. Hopefully some of this helps.
