My intention is to stay in the marriage. My hope is to reach a point where I'm not feeling as "strained". It already feel much less uncomfortable than at the beginning so I'm hoping it continues to get easier. She has apologized and still cringes at a lot of her NRE behavior, and is trying to do things with everyone in mind.
Then it sounds like you are both in this still and still willing to do the work required. What about the missing voice? Her Other Person? Is this person on board with moving the polyship forward to a healthier zone or not? There's more than just you two on the crew of this new polyship mission.
I see this as everyone at the square 1 place of "Your mission, should you choose to accept it..."
So do all players accept the mission? Are all players in agreement what the mission IS? (I am assuming the mission is a harmonious "V" shape configuration where she is the Share Sweetie hinge person.)
You guys sound like you are choosing to take this like some turbulence in your life journey together and are trying to make repairs required and get back into flying straight up. Not just with each other, but with a new crew member.
I do not know if it could help you, but I wrote my personal standard out --
scroll to the bottom. That's how I want to be treated in relationship. That's what I'm willing to give in return. So DH and I can be in right relationship to each other. It makes it easy to hold him and myself accountable -- am I doing my responsibilities? Is he giving me my rights? And vice versa?
Perhaps this could be opportunity to (re)articulate and (re)affirm what the standard will be in your own relationships? Not just (you and her) on that tier of your polymath. But in all your tiers of relationship with her as the hinge person and your metamour? Can you create your relationship standard banner you all can agree to fly under and honor? A new person in the mix would be expected to review it and add their own things so it can become the thing to serve the needs of the new crew and all can be in agreement.
Could that help smooth the way? You still can't know HOW it will work out or even if it does on this new ship you are building. But you could come to agreement on how you want to be treating each other in relationship on board as you get to wherever it is this journey is going to next -- the harmonious V goal.
You are in the interesting position of having to build the ship while already flying it! This is your reality. It's good you see that and accept it for what it is. Could choose to remember that and try to forgive each other along the way if things get uncomfortable at first as you try to find "the new normal." It's bound to feel weird at first.
Are you guys considering a poly-friendly counselor?
This is an
older thread about a different 3 people triad situation who face broken agreements, conflict resolution, forgiveness/making amends, and rebuilding trust.
You have a different 3 people shape arrangement there. But the breaking down of the elephant in the room, and owning bits of it? Elephant is just elephant. Maybe reading that thread could help give you guys some helpful nuggets that could be use in your process as you guys break down your OWN elephant problem?
What could you need most here for yourself in terms of "forum people support" as you sort yourselves out over there?
HTH!
GG