Well, that is a B%#$H and no mistake.
If the relationship has been a bummer for the last 15 years (Think you called it strictly "business" for the wife......) can't imagine how you made it this long.
Look at the bright side. You won't be in a "business" relationship with your significant other.
You are an excellent knife maker! Love your stuff!
Could be worse. You could be some one with no discernible talent, and looking for work.
What I hope for you, is that doing the knives full time will be far more fulfilling than working for her parents, just for a paycheck!
On a side note, hopefully, you get a decent attorney, and the fact that you are loosing your income as a result of her family business thing means she will owe you support!!!!!!
Make sure your kids know you love them, and it's not their fault at all.
Good luck!