Hello and welcome!
It sounds to me as though all three of you are in a high emotional state right now and have a lot of thoughts and feelings to work through.
Stop. Breathe. You are not going to solve everything all at once. To me, it sounds like your husband is pushing things rather quickly - and then gets upset when things don't go as he envisioned. This is new and you and your husband are going to have to learn a lot of communication skills and be able to talk about things without emotions getting out of control
As to this other girl - she knows that she is looking for a primary to settle down with. He is not available for that. I think he needs to back off and let things settle. Back things down to friendship+feelings and let it ride.
PS. If you are still in the 12 hour edit window: you will get a lot more replies if you go back and add some paragraph breaks to you post. A lot of people have a hard time reading a long wall of text and will skip over posts that are too hard to read.
Me: poly bi female, in an "open-but-not-looking" V-plus with -
MrS: hetero polyflexible male, live-in husband (24+ yrs)
Dude: hetero poly male, live-in boyfriend (5+ yrs) and MrS's BFF
SLeW: platonic girlfriend and BFF
Lotus: "it's complicated"
+ "others" = FBs, FWBs, lover-friends, platonic G/BFs, boytoys, etc.
My poly blogs here:
The Journey of JaneQSmythe
The Notebook of JaneQSmythe