Look, it's obvious you're a nice guy and trying to be as giving as possible. But there's a guideline in poly to go as slowly as the person who is most uncomfortable needs. It's not a rule, but you'll see lots of reference to it in these threads. It's not about controlling her, it's about mutual respect. She can slow it down as a way to respect your discomfort. Some people need to just be okay with their spouse just holding hands with someone else first. That guy's (or another's) penis will still be there when the two of you have gotten more comfortable with the whole idea. Why put up with something that has you so upset and then wait til afterward to tell her?
You said in your first post in this thread that you are happy to see her happy but that "damn near close to tears that it is no longer me." The fact that you think it is either another man or you that would make her happy, and not having two people who could potentially make her happy equally, tells me you have some issues to resolve before diving in. Poly makes it possible to love and be satisfied with more than one person, not choosing one at the expense of the other!
Unless you two are just after sex and swinging with no emotions involved, slow down! There's nothing wrong with casual sex in my opinion, but it doesn't seem like you're ready for inviting that as an element in your marriage yet. Polyamory requires thought and respectfulness for all involved, not just deferring or submitting to one person's will in the relationship. You're not her owner, but you are her partner!
Why not invite her here to post as well? Would be good to get both sides here.