best of luck to you! i'm new here, too.
i'm a little curious, though: why aren't you going to tell him you are researching this? or at least broach the topic?
i mean, you obviously need some time to get your head wrapped around the details, sort out how you feel, and learn whats out there - wouldn't he need that, too, before a serious convo could take place?
seems to me that it wouldn't be that hard, since you already have something that is more "open" than traditional marriages. you could just say "this situation is unusual, and made me question if it was polyamory and what polyamory is. i don't know much about it yet, but am researching. maybe you should do the same, and later we can talk about it?"