I'm glad you could join our forum.
"Sooooo ... how do I best work through this so everyone can be happy, be themselves, and enjoy life and the kids?"
I'm afraid you may be trying to solve an impossible problem. Your husband and his ex-wife don't have compatible feelings about what they want from each other, and these are the kind of feelings that have to do with chemistry, they aren't customizable, let alone by anything you do since you aren't in that dyad.
The only hope would be for your husband to explore the reasons why he doesn't trust her, and see if there is any way to rectify the root causes of that mistrust. Maybe if he trusted her more he would be more inclined to relate to her romantically. All of this would take a lot of work and cooperation on his part though, and she might have to do some things to restore the trust as well.
Things like bits of jealousy over her nights with him, and her reluctance to share, are emotional states that may fade away over time. Sometimes it helps to communicate (such as a three-person sit-down) about these feelings, not assigning blame, just getting them out there. It may be a good idea anyway to have regular sit-downs (such as once a week or once a month), especially in the early stages of your triad relationship.
On the other hand, if she continues to not want to share, and that feeling becomes more instead of less intense, then you could be headed for a nasty break-up somewhere down the road. You're exposing yourself to a certain amount of risk by venturing further into this triad relationship. It looks like you're already committed to it though, so I guess you'll have to see where it leads.
Perhaps you will benefit from the Life stories and blogs board
, where you can observe experiences other people have had with poly, and what has and hasn't worked for them. Plus the Poly Relationships Corner
is a good place to post further thoughts, questions, and concerns.
I am sympathetic knowing you just want everyone to be happy and are trying your best to be helpful to your companions. I wish you well in your endeavors and hope this post helps in some small way.