This thread has been odd to read because for a while, I was in a similar situation to your man, and I sympathized with him on reading your OP. Until not long ago, I was going out with a bloke who was separated and not yet divorced, who didn't seem that bothered about GETTING divorced although it was clearly over between them, and who allowed his ex (who was pretty nasty) to walk all over him. There were no set times or days for DC's contact in place, so she would just mess him about so that he was running round according to her whims, she changing everything at the last minute and him often having to cancel on time to be spent with me because she had suddenly decided she couldn't have the kids after all and would send them back early. And she'd never commit in advance to having them, weeks would pass without them going to their mums, so I never knew when I would next have time 'alone' with him. It was a long distance relationship and his kids are quite difficult and demanding, so if they were in the house, a normal phone call or webcam chat was pretty impossible as he was interrupted every 2 minutes consistently. I never knew where I was with him, and it was so annoying having to watch this bloke (who I loved) allowing himself to be used and dumped on from a great height. I frequently expressed this to him and sometimes had to take a step back from the situation, because it was maddening to watch and soul-destroying to be part of.
So when I read you OP, I was all understanding for him and, 'poor man, I can see his point of view', etc.
But then I continued to read the thread and I did a bit of thinking. And I realized that no matter how frustrating I found my blokes ex, or his 'tail between legs' attitude around her, I had never issued any kind of ultimatum. Why would I? It was me that found the situation maddening, so my problem in essence. When I stepped back, this was always what I said. I frequently apologized for my inability to cope with what seemed very normal and run-of-the-mill to him. At no point did I tell him what he should do and that if he did not, he would be punished by me in some way. What kind of loving partner does that?! Good grief. If I didn't like the set up, I could leave. And I did leave in the end, because it was ultimately too frustrating for me, and I realized that he wasn't going to change. It was my problem, and he shouldn't change his behaviour to accommodate that.
Your fella... I know you think he's protective of you, but there is protective ad them there's stifling and controlling. He might think he has your best interests at heart, and maybe he does! He probably really loves you a lot, and can't bear to see your ex in your life after what he did to you. I can understand that.
HOWEVER, in his demands and emotional blackmail, he's revealing implicitly what he thinks about relationships and how they work. He's revealing a part of his character. It's not that he's being deliberately controlling of you, sitting there rubbing his hands, gleefully cackling 'How can I further enslave her! Muahahaha!'. He's just a controlling person. Unwittingly, inherently, implicitly, but he is. He's just revealed this to you. So listen to what his behaviour is telling you, or you'll regret it later.