Your xh is jealous and resentful of all that you've accomplished and doesn't like the fact that you and the children are happy and that all of you are living as one big happy family w/the NG.
As for the health issue, he may be using emotional blackmail to get the children to stay over on Sunday nights. Even if he's got a health problem, that doesn't mean he "has" have the children on Sunday nights. I would think he would want some peace and quiet after they've been there to visit.
He's just not a happy camper and will do whatever it takes to try to ruin your happiness and one way to do that is thru the children.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
