Jesus. Falling over yourself to be first comment were you? First thought pops up, bang it out and press post without any consideration for the context or whether your remark would be in any way appropriate or helpful? But first though, so well done you.
So sorry, OP - this is really shitty and sad. It does sound like he’s way ahead of you and you need to catch up and get on the same page as him, which is difficult if you’re bewildered and in shock.
The fact this is a big birthday is bound to make you feel worse, but don’t let it engulf you. I’d be inclined to park the 40th for a minute - it’s really just another day - and concentrate on the things that are going to actually make a difference to you going forward.
Taking action to protect yourself and your children, getting your finances and legal position in order, gathering your allies and support network, understanding your rights.
Because when all of that’s done, you can have a proper celebration. You can and will get through this, and when you come out the other side - whenever that may be - you can do whatever the hell you want in whatever style you want to mark the occasion. It’ll be better than 40, it’ll be a celebration of the future and everything that’s still possible.
Forty is young. You’ve got lots of life and happiness ahead of you 💐