Hey y'all. First time in the sub, but have been thinking about this topic for quite some time. A bit of background first, but feel free to skip to my question below if you prefer.

Background

I (M39) have been married to my wife (F38, she/they) for 15 years. We have both deconstructed from evangelical Christianity in the past 5 years, and were products of the associated purity culture movement. I'm the first and only person my wife ever dated, we shared our first kiss at the altar, and have only ever been sexually intimate with each other. Our intimate life never really clicked, with the only time we were ever having frequent sex being when we were trying to conceive our two kids. Since we found out we were pregnant with our youngest over 8 years ago, sex has been very few and far between, and I haven't once had an orgasm during one of intimate sessions, which often seems to go off the rails while trying to get her comfortable during foreplay. As we've gone through our deconstruction journey, we've learned more about queer sexuality, and my wife has come to understand herself as asexual. This makes a ton of sense to me, and I love and support her in discovering this identity, but it has continued to leave me taking matters "into my own hands" on the regular. There are a variety of other medical and emotional reasons physical intimacy is complicated for us, but to sum up, we're in a dead bedroom situation, are in couples counseling, remain firmly committed to one another and our family, but I'm feeling a high level of dissatisfaction with a lack of sexual intimacy with another person, especially as our new world view has opened my eyes to the beauty of a sex positive perspective.

Current Situation

In the past couple of years, we've become very close with a number of queer friends. One of these couples are poly, F and NB. Their relationship is new enough and they've had some major life changes recently, so they aren't currently open, but it seems like the expectation is that they likely will be in the future. I've had some opportunities to hang out with the female friend from that couple one on one, and feel like I'm drawn to her in some significant ways, though nothing physical has happened or even been hinted at. As a cis het male who is new to queer spaces, it's tough for me to tell if that vibe is mutual, or if this is just openness and depth of queer community that I've been missing in more conservative social contexts. Even if my wife expressed total support of us opening up (which would shock me), I don't think I'm ready to start dating random people, but the attraction to this friend has been hard to shake for a bit now. If this attraction were reciprocated, I am certain that both of us would be in support of setting boundaries to keep our primary partnership as primary, but possibly explore a deeper intimate connection if our partners were fully informed and consenting.

Questions

• I'm sure opening up initially as a FWB scenario is all kinds of complicated. Any advice from those with experience about issues/questions I should be wrestling with before taking any action?
• My wife and I have never talked seriously about opening up, although it's been an ongoing joke that most people who know our friends are poly probably assume the four of us are in a situationship based on how close we are. My wife and I do have plans to talk about our intimate lives at our next counseling session. Any tips for gently broaching the subject without just flopping all the cards onto the table? (which I could easily see as going poorly)
• As noted above, my friend's relationship is currently closed, and this is the only person I would currently have an interest in opening up for, so nothing is going to happen in the near term regardless. That said, is there wisdom in trying to gauge if the attraction might be mutual before even tip toeing into the discussion with my wife, or does that risk back firing if/when she finds out I've already discussed the idea with our friend before talking to her?

Sorry for the extremely long post, and TIA for any advice you have to offer.