I think if I were I your position Fidelia I would tell him what you have said here. Minus what you think of how he does his religion maybe. He doesn't need to know that part and won't benefit much from it. Its just a preference you have and really and it could take away from your point.
I think that if you are a good friend and intend to be more of one, then tell him that his over talking comes across as having an overly large ego, that he maybe should look at whether or not he could allow others to finish what they are saying and come to the forefront by waiting his turn to speak or using his big voice to offer space for others. Maybe there is someone in particular that doesn't get a word in and he could see to it that they do, but using his voice to advocate for them having a voice.
As to poly; I think you could say what you said here. "I know something about polyamory. Do you know it? I'm not interested in you but ... " might be a good place to start.
I am wondering if maybe you are over thinking. When I get stuck sometimes I ask myself what I would say to someone on the forum if they wrote on here. Some things become very clear at that point. Maybe that would work for you?
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