I don't know what to say.. because something very similar has happened to me. It is betrayal and yes I'd say it is abuse. He has turned their heads, they have jumped ship to the more powerful one. He has very probably lied to them - oh so subtly (or maybe not..) - about you. He has seduced them - his life and what he has to offer is very attractive..
I'm afraid I'm still in the immense shock phase but if I could talk to myself at the beginning when it first happened I'd say dust yourself off and RISE UP. Don't be the victim but rise up. Put that light on, get up, stand tall and look them straight in the eye. Get straight. Think kids when they play you up, get firm. Don't appeal to them bcs it makes you look weak - and the last thing you need to be is weak bcs it is weakness they currently despise (bcs they have been seduced by powerful him). I don't mean be harsh or fight but be straight. They can fuck off if they think they can throw you away like garbage bcs they've had a dazzling offer, especially with all you've done for them (as any good mother would). He's behind this, the skunk.
BUT they are adults and there is no excuse for this behaviour. Girl, you're going to need to be strong - fake it till you make it. I mean it. Your life depends on it. They are not your life or your company - yes this has been brutal but build your own life now. It's the order of things that kids fly the nest when the time comes - admittedly, we didn't quite expect it to be as brutal as this, genuinely expected our kids to be generally in our lives to some degree, not take off once they'd got what they wanted. Get a glint in your eye.
Phew, talking to myself there haha (not that it's funny, there is nothing more painful on the planet imo).
As for money, yes, it's the order of things that once the kids go you lose the finances that come with them. BUT you should get spousal maintenance - and, as you are married and he doing very nicely thankfully, you should get a good settlement (tho his partner's income won't come into the equation). Don't be beaten by his threats, he is not greater than the law and he will have to comply - tell your lawyer he is blackmailing and intimidating you.
Be bold, be strong. Our kids are being bullies just like their father. Don't EVER show weakness to a bully, even if you break your heart in private.
You CAN do this! In fact, you must 