The teenagers aren’t allowed to fly alone
Why?
BTW, I have flown with an infant and a toddler and no other adult. It's pretty common the in expat community.
The high income and ex thing is something you will most likely understand better in a few years. Clearly, being married to a high earner requires a lot of sacrifices. You've started making them, and you'll find that as long as you are married to him you will keep making them. So you need to decide if that is what you want.
His ex made sacrifices for years. She wants her children with him to reap the benefits. Chances are, you will too. International moves can make it easier to hide money, so divorces/maintenance/child support can be very contentious.
I suspect that if you keep being so difficult, you marriage will fail. He's divorced wives and left children before. His mother is difficult, and you knew that when you married. It's one thing you and his ex have in common.
If you want actual marriage advice, I've moved 11 times for my DH's job and understand the international moves better than most people. I'm a first wife, so my sympathies lay that way. But I do understand the situation you are in and how difficult and lonely it is. None the less, fighting with your DH about who gets stuck with the 2 year old is NOT the solution