First, I don't think bringing it up when he's drunk is such a good idea. You need a serious talk and he'll need to be on an even playing field with you, if you bring it up when he's "diminished", it's like you're giving yourself an unfair advantage in this discussion.
Secondly, the fact that the person you're interested in already knows you're intentions before you brought it up with your husband... is not so good. Now, it's great that you haven't cheated on him, but from his point of view, maybe you already have: you went behind his back to arrange things with another guy, rather than discussing things with him when you started having feelings, he could feel very betrayed.
So I think after you bring it up you might have to earn his trust, and you could have to say goodbye to your plan of getting together with that specific guy, and do it when your husband is actually involved in the decision before the fact, which might make him more secure about it, and not feel like it's already decided and if he says no he's losing you, so he has no choice.
About the feelings of "ickiness", I guess you need to really think about what you think might cause them. Insecurity is indeed a big thing for a lot of people, and if you're not a very confident person that could be it. You could be scared of comparison, or just feel like you're losing a "possession" by "sharing" someone.
Either way, you'll need to come to terms with it first, just like your husband will have to come to term with his own hangups, if he does want to work on them, of course.
But if you want him to actually have a voice, and be part of the decision, I don't think cornering him into the discussion is likely to make him feel appreciated. I know it's a difficult discussion to have, and it's hard to bring it up, because I was in your shoes once, but you risk hurting him if you don't go into it thinking about him as much as you can, and putting aside for a moment your fantasies about your ideal relationships. Most partners need time to be willing to get into it, when I brought it up it took over a year before anything happened, you need to talk it through, talk a lot, and be clear that you love him and want to stay with him no matter what.
Or, if you think poly is such a part of you that you can't live without it, then be prepared to leave him if he's not fine with it. And I would advise against letting him go with it "so he doesn't lose you". It's a very toxic way of thinking, if he goes into it thinking that, it's probably best that you do break up because I can't see a lot of good coming out of it.
...A bit more of a rant than I originally planned. Either way, let us know how things went after you have the talk.