Thank you all. Your responses have been awesome and have helped a lot. One other thing to mention -- this desired-after "triad" of sorts wouldn't really be a true full-time relationship. At least not for quite a while. We both have busy lives and family and friends we see often, events, holidays, etc. This would almost be a continuation of what it is now - with maybe the added knowledge that it is "something" - not just a trick we have over sometimes. Maybe I should stop trying to find a label for it? Ha.
Oh, and I DID just buy Opening Up on audiobook, and Ethical Slut through Amazon. Ha. :-).