Take a break from trying to reason with STBX about this. You say you are going to, but you don't. He told you that he would listen to C. GIVE HIM A CHANCE TO DO SO.
YOU need to listen to the C too. Indeed, before or after he has a session with the kids' C, you should to the C as well. Talk about your fears. Ask about the frequent texting and phone calls from you on STBX's days with the kids. Ask about whether it is more harmful to disrupt their R with their father or to allow them to transition to a blended family too quickly.
TAKE A BREAK from managing STBX and try to get some objective perspective on this. See where you are after S, STBX, and YOU have all met with the C.
Then, if it seems appropriate, take what C tells you and talk to your L. Then, try to change the agreement if it makes sense to do so.
This wrestling with STBX is not helping anyone. It is unproductive and is truthfully starting to sound like hounding. If you disrupt the D process you risk making things worse for you and the kids. If you are going to make the D ugly, he may as well too. If you can change the agreement, he can too. Maybe he'll require zero contact between you and the kids on his days. Who knows what he'll decide to try to add to the agreement.
You have got to let go of this for a few days and see how things work out after C. I know it is hard. I know that you are 100% right that STBX should be doing things differently with the kids. But this obsessing and controlling behavior is NOT going to help you or the kids. Let everyone see the C. Get an objective opinion on how best to proceed. See the L. THEN finalize your strategy. Flailing around in a tantrum right now risks closing some of your options and narrowing your choice of strategies. TAKE A BREAK. GET SOME OBJECTIVITY. DON'T HURT YOURSELF OR YOUR KIDS.
