Well I read the entire thread. Great thread!
I think that you have a right to be upset and I'm glad your husband understood your feelings. One thing I would suggest, being married myself, it's more important to me that my husband understand boundaries, rules and limits than some random woman who is only out for herself. I suggest equipping your husband to "check" women so that you won't have to. People are always going to test the line and cross it - if we allow them too.
When I'm uncomfortable with a behavior from a female friend (of my husband's or just myself) or vice versa, we discuss it with each other. It's not always easy or painless...but it has to be done. That way WE are equipped to deal with it and don't have to come off looking "crazy" to someone of the opposite sex. So all I'm saying is it may be a good time to talk to your husband (if it's even needed now...not sure it is) and discuss "emotional affairs, boundaries, limits and what's appropriate for you guys as a couple". Also make sure you're preaching what you teach.
I really feel like your husband's first reaction when this woman called and said "get over here now" should have been, "Hey hun, so and so just called with an issue and her husband's not there, so why don't you come with me."
That would have solved a huge problem right there.
Lastly, I'm sorry this happened to you and I hope that you guys develop healthy relationships elsewhere, cause something was def off with that couple.