Happy Birthday to your son! Hope he had a blast and got lots of pressies.
Your XH seems to have no idea how it works. Don't succumb to any threats to litigate for for 50/50. I suspect they are entirely hollow and an act of bravado.
If property will be protracted now, see my earlier comments about severing the joint tenancy (if applicable), new Will etc. I think I mentioned this months ago. That said, him engagaing lawyers doesnt mean it'll make things go bad - keep PMA, ok.
If you're continuing to communicate with XH direct despite both having lawyers, you may want to speak to your L about whether your comms to him should be without prejudice. Frankly, I'd leave it to the lawyers to communicate on your behalf given your sitch.
With the email, I'd delete reference to S having a wonderful time etc. Remember, it's business now.
Keep taking the high road Scout and accumulating karma credits. Good luck with it all and stay strong (if not dry lol).
Me: early 40's XW: nearly 50 T: 15 M: 5 BD: Jan 19 S:10 SS: 22 SD: 24