Well, four months later... I figured I'd update. Bear with me, this is going to be long.
There's a lot of good and a lot of bad to report. I went away with the friend for a weekend, and things turned sexual. The whole concept kind of blew his mind, since he's lived in pretty traditional environments for his whole life. When we got home, my husband talked with him, confirmed that he's okay with it, laid out some boundaries, etc.
Ah, but if it were only that simple. Fuckup the first on my part: I inadvertently chose a bad time to spend the time alone with the friend (I'm just going to call him BF, though it's not exactly that official). DH felt pretty abandoned/neglected, and I could have done more to reassure him while I was away. The trip was originally going to involve a couple of other friends, but they backed out, so it just kind of happened. Not a good start to things, but we worked through it pretty well.
Shortly after this all happened, I also had a few revelations. For one, I realized/fessed up to the fact that I was really attracted to BF on more than a sexual level. I acknowledge this is due at least in part to NRE. However, I also learned a lot about him once our intimacy ratcheted up, and realized he exceeded my expectations about him. I am a generally accepting person but also usually expect people to let me down at some point, to have a critical fault that makes me go "And thaaaaat's why I'd never be with you." Well, that "safety valve" isn't there with him, so my emotions got more involved than I thought they would. I absolutely love my husband deeply, but I feel more "in love" with BF right now. My love for my husband is a mature, comfortable, known love, while my attraction to my BF contains more excitement, newness, and that thrill of getting to know and love somebody. I totally understand why this is upsetting to DH, but I'm also not quite sure how to feel differently... or even if it's possible... or even if I should.
I also realized that there were a lot of things I saw in BF that I USED to see in DH, but that he'd let slip away because of general dissatisfaction with where he's at professionally/depression/etc. This was probably another major fuckup on my part, but I was brutally honest with him about all of these feelings, and told him that I really needed him to work on his self-esteem and self-efficacy because I didn't want to find it so attractive in someone else and know it was lacking in him. I realized that a lot of my happiness in life, which I had attributed to our marriage, was really happiness with myself. That's all well and good, since I do think you should be happy with yourself first and foremost, but all of this led us to a difficult place.
Sometimes DH thinks my relationship with BF is awesome. The sex part turns him on, and he tries to feel compersion for me. They are friends and generally get along fantastically. Oh, BF also became our roommate, largely by DH's suggestion/request, and that has its plusses (I'm not 'ditching' DH to go spend time with BF) and minuses (less privacy for either "couple", more access to BF than DH would like...). So.
When things are good, they're great. When DH is happy, I feel like the happiest, luckiest woman in the world. I love my bizarre little family the way it is. I love how the two of them complement one another (and me). There is a lot of overlap between them, but they also fit like puzzle pieces when it comes to areas of strength/weakness. I think betwixt the two of them, every single characteristic I'd seek in partners is met.
So, the downsides: I kinda suck at this. I moved too fast for DH's sake, and I know it. Once I got the ball rolling I didn't really know how to slow it down, and dragged DH along for the ride. I am trying to keep things straight and level where they are, now, and step back a little bit in the sex department to keep things at a semi-comfortable level for him. DH is very sensitive to the timing and frequency of sex with BF, and hasn't always been able to communicate what the right thing for me to do is. For instance, I thought it would be better to have sex with BF when he was home mid-day and DH wasn't around; however, DH saw that as BF getting me at "my best" while DH and I usually have sex in the evening when we're more tired and ready for bed.
DH is also really not pleased with the emotional connection, and I fear this is the part that will be the downfall of my little dream world, one way or another. I accept responsibility for this, as I had knew he was essentially open to swinging, while I was open to polyamory, and I proceeded with what I want faster than he was ready. Not cool. His brain does not work like my brain. In his mind, people are on ladders, they are ranked, tallies are kept. He thinks there is only room for one person in a primary spot, and he wants me there. He is very worried about being my primary, and that I will love BF (or anyone, for that matter) more than I love him.
I honest-to-dog do not think like that. I have explained the way I view love until I am blue in the face. He is trying to make something scientific of a supremely unscientific thing, and I don't know how to reconcile that. I don't have some sort of love-matrix I lay overtop of a person and figure out how they stack up in columns A-Z. There are things I adore about DH, and things I adore about BF, and a lot of things they have in common, and I think these factors make them both capable of reaching that special place in my life. However, DH absolutely cannot accept the idea of someone being "more," and he cannot comprehend someone being "equal." He doesn't think it's possible, and I think he also sees it as him being bounced from the "top spot" to be brought down to someone else's level, as opposed to that someone being elevated.
BF has been pretty insulated from the impact of this on my relationship with DH. When DH was upset after the first weekend with BF, I told him I wanted to keep it between us, because I had just come off a weekend of insisting to BF that it would all be fine, DH was onboard, etc., and since he was kind of confused/conflicted, I didn't want to land him right in the middle of some drama. To be honest, I am not sure what level of communication it is appropriate to involve him at, since the root issue (whether DH and I can see eye to eye on what we want out of a partner/partners) isn't really about him. I think he would blame himself for causing problems, and I don't want that.
DH and I have been together seven years, next month. We have a young child together. I love him very, very much and he is my best friend. I will acknowledge I am experiencing NRE with BF, but I have a great connection with him and believe I will/can/do love him very much as well. DH and I are very philosophical, thoughtful people, and we place a lot of value on what the other person's ideal world would look like, even if that ideal world can't come to pass in the real world. I don't know if that's a mistake, or not. We have also been trying to find the line between control-demands and condition-demands; neither of us claims ownership of the other, but we acknowledge there are certain needs that must be met as conditions of the continuation of our relationship.
For him, it seems the chief demand is that he be my one and only "primary." I completely understand not wanting to be a clear secondary. However, I just don't know how to reconcile his need with the fact that my head and heart don't look at people with the kind of hierarchy he wants to be a part of.
Anyway, I don't really have any questions, though thoughts would be welcome. I am mostly just trying to organize my own thoughts and get them out there to folks who can at least kind of understand. We are almost 100% closeted about this within our social circles.