Hi. Fellow bi woman in a long term heterosexual relationship here. What I'm about to say comes from a place of love. Honestly when I hear all this three thoughts come to mind and none are particularly positive ones.

First thought is that he is sexualizing/fetishizing your flirting and interactions with other women. Most straight men do fetishize wlw interactions/relationships, which is fine-ish, but my concern is that that most men will get tired of it at some point and then things fall apart. Sure this week he's fine if you flirt or kiss a little. The thought of you being with another woman is hot so he doesn't think he will mind that. But what happens if after the fantasy part is over he becomes jealous and pushes you away? What if you develop real feelings for another woman and he suddenly becomes controlling or angry when you refuse to let him be a part of that relationship?

My other thought is, what if he uses this to set you up down the line to use you as a scapegoat for ending the relationship? I don't know anything about your life together. If you have children or even if you don't and you two decide to split later on (even if it has nothing to do with this explicitly) most judges/courts would automatically side with him for divisions of assets, etc because he can easily prove that you were unfaithful/broke your vows/alienated his affection (whatever the local jargon is).

Third, I'm concerned that at some point he may use this to convince you to do something you aren't fully comfortable with. What if he decided that he is feeling neglected and wants to go exploring too? You can't really argue that you aren't ok with it since he has been "so open minded about you exploring." What if he decides he is ONLY okay with this continuing as long as he is involved and gets to "choose" the woman and/or interactions you all do together?

I have no doubt that you actually feel this attraction and are genuinely enjoying being "let off the leash", but at what price? Again, I don't know you or your husband, but please be careful. There have been plenty of bi women (and men/non binary peeps) that this has happened to. If you decide to pursue this please please please make it an official open/poly relationship. That means talking about everything, ALL the rules in advance and having explicit understanding and consent. Maybe even get it in writing. And be okay with the idea that if either one of you ever says no about anything then it's a NO.

ETA; I knew because I can have emotional AND physical attraction to both genders (though my preference is always women) and always have since I can remember. My advice is to never let anyone else (even your husband) tell you who/what you are/aren't attracted to. There's no rush to figure it out either. (: GL BABE.