I have so many mixed emotions. More than I expected.
I need advice on what to say, how to feel! AHHHH!!
-TNC
Dear TNC,
I'm quoting from your first post, even though you've progressed so far since then. May I congratulate you for the great way that you're dealing with all this?
Although I haven't been active on here for some time, I still consider myself the Site Pedant, so let me correct a detail in your first post:
"I have been trolling this site for a while". You NEVER trolled this site. Trolling is writing nasty comments

, trolling a site is writing nasty comments that are viciously opposed to the whole feeling/philosophy of the site. You were
trawling the site

.
Now let me introduce you to 2 [British] polyamorous terms:
FRUBBLE: A pleasant emotion of happiness arising from seeing one’s partner with another partner.
WIBBLE: A feeling of insecurity, typically temporary or fleeting, when seeing a partner being affectionate with someone else.
It's very possible to feel wibbly and frubbly at the same time. Since you wrote
"I have so many mixed emotions", I wonder if wibble was one of them. Nothing to be ashamed of, and it's best to talk about it honestly, along the lines of "I DO want you to do this, but there's this little bit of..."
Her boyfriend is a really nice guy too and although we are not close yet, we are both very respectful of one another. I see him when he drops my wife home or when I drop her there and we have even had a drink once.
I think as time goes by things will get ever better and we might even take a trip together. Any advice on that from folks in a similar situation. Should we prepare to get stares or weird looks if we go out together as a trio or thruple or whatever the term is??
Prepare to get stares or weird looks, prepare to get jealous looks, as well... or just decide that it's really nobody's business but yours, and if other people have problems with that, well, other people have problems.
You've already started on a trip together of a much more important kind than a physical, limited-time, geographically-defined one. So go for the latter as well... and have a great time together!
You are REALLY lucky that you two men respect each other and get along well. I think that you should get to know each other as much as [comfortably] possible. Knowing just who he IS is going to help your communication with your wife. Caring for him as a person is going to help things all around.
Others have given you good advice about finding another woman who can deal with your situation and fit right in. But - at the risk of sounding like a downer (which I'm NOT!!!) - I think it's only fair that you should consider a POSSIBILITY. And I'm afraid that it happens more often than one might think.
A+B have a long-term mono relationship, decide to go poly.
A starts a relationship with C and it goes well.
B has mixed feelings but deals with them fantastically and becomes friends with C.
A+B+C have a few problems to smooth out, but it IS working and all 3 are happy that it's working.
B starts a relationship with D.
And all Hell breaks loose. A discovers that (s)he isn't as polyamorous as (s)he'd thought. A gets wildly jealous and either
a) demands that A+B return to monogamy

, is willing to give up C as long as B breaks up with D;
b) breaks up with A

;
c) [worst case scenario] demands that B NOT have a relationship with D, but reserves the right to continue with C

.
However remote this possibility might seem to you (after all, your wife is a wonderful, loving, open, fair person), I think that you should talk about this REMOTE possibility before you take the plunge. After all, you talked about her other relationship for a long time before SHE made the first step, didn't you?
A big, warm hug (and a high five),
MFFR