I think there's a lot of good advice and observations in here; I especially like the comparison to your husband wanting to learn something new, like painting, that Tonberry offered.
As for the more recent "wobble;" have you talked with either/both of them about what you are feeling about what happened that night? Poly doesn't work without communication, and while there might be a middle ground between you "chilling out" and your husband being more thoughtful, that middle ground can only be found if you talk about it. It seems like you really care about your gf, and you clearly love your husband if all of this is on your mind, so it's worth talking about. Ask him if he's feeling any of these things, and if you need it, ask him to provide you with reassurance from time to time of your importance to him. We all need little reminders now and again of how wonderful we are.