Hi and welcome. You know, as I was reading through your initial post, I had the sense that you and husband don't need to worry too much about what polyamory is or about certain ideas that come out of the poly community. I thought that before I came to your post saying that you probably wouldn't be comfortable in a poly group setting.
Of course, this forum is a great resource for information, and the term polyamory is useful for finding other like-minded folks. Personally, I don't identify as polyamorous, I consider the types of relationships in which I want to engage to be polyamorous. I'm just me.* And I don't really even like using the term polyamorous. But really, no one can tell you how to "do" your relationships and it seems like you have simply discovered something new and wonderful for yourself, for which you simply have no previous frame of reference in order to know how to proceed.
If I were you, I would try not to get caught up in what's poly or what's mono. Your husband wants to focus more on broader aspects of this development - what does that mean, exactly? Everyone conducts their poly involvements differently. Some people are partnered and open to flings, and others are polyfidelitous. AND you don't have to
belong to a greater poly community, participate in poly activities with other poly peeps, read all the books there are on poly, nor seek out additional love interests to live a life in which you have more than one, committed, ongoing, loving, intimate relationship. Sometimes things like this happen and you just go about your life and manage it like you would any other friendships. However, obviously, any emotional reactions to either of you wanting to be sexual with someone outside of each other will demand more attention and care than a friendship will.
What is important is listening to your heart and to each other, and to be as loving and caring in how you handle this new wrinkle in your life. I don't think that pushing your husband into reading about poly or going to poly events will be very useful or helpful right now. This is something huge for him to wrap his brain around and, although you can let him know that you will not just let it slide and disappear, I think giving him time to let it sink in is the right move. I would be careful not to harp on the issue too much (not saying that's what you're doing, but it's something to think about), as that will become irritating and cause him to get defensive. Just shower him with love and let him know that that will not change.
It seem you have lots of intelligence and common sense, as well as some real understanding of your needs, wants, and emotional life. Be patient and allow hubby to process this while keeping the lines of communication open. Perhaps, when he seems ready, you can just get together with him and the BF, in a social way, so that they get to know each other a little better. He might feel better about you being involved with the BF if he knows him and can trust him as a friend himself.
"There aren't polyamorous and monogamous people; there are
polyamorous and monogamous relationships. The same person may
at various times be happy in both monogamous and polyamorous
relationships at various times in his/her life. What is right
depends on you and your feelings, and the feelings of those
you are involved in relationships with. You may at some times
be involved in a relationship that is monogamous, and that
may be the right thing for the people in that relationship;
at other times, you may be in a relationship which works
better as part of a polyamorous network of relationships. In
any case, the important thing is probably to act kindly and
responsibly, and to communicate clearly with intimate
partners and potential partners about these issues. Don't
deny your feelings or the feelings of those that you care
about. Get in touch with how you and those you care about
really feel, rather than how society wants you to feel, or
how you think it would be logical to feel, or how you've been
told polyamorous people (or monogamous people) should
feel. Then behave in ways which are honest, and which make
you, and the people you care about, and the people they care
about, happy and fulfilled. If this results in you having
more than one intimate relationship at the same time, or
being involved in a relationship with more than two people,
those who are big on categorizing and labeling people will
label you a 'poly person'."