I agree with DnJ (as usual). I think it's a wonderful sign of your strength and love for your mom that you allow your exH to be there. If only we could all focus on something more important ALL the time, we would not freak out in the presence of our spouses. I just love how your love for your mom is so powerful that it overwhelms everything else, like the sun of your love for your mom and your knowing that your kids need your exH next to the lightbulb of your anxiety about your exH. I hope that this will continue to bring out all your best selves, including your exH's. There is so much love radiating in your posts about this, it is powerful. Your grief will be hard but the rest will carry you.
I believe I will see the bounty of the Lord in the land of the living. Wait for the Lord with courage. Be stouthearted, and wait for the Lord.