How does this wife act around their own children?
15 counts of child abuse and the loss of her other children, and then, suddenly, she's a good mother?
IF she is a decent mother with their children, and just reviewing the other circumstances that you have described, I simply cannot make the leap to the conclusion that this wife is about to put out a contract on your friend.
Everything that you describe the wife doing in this marriage is probably more typical than you can imagine.
You can go to the authorities with the evidence of forgery, but, I seriously doubt that they will do anything at all about it.
They will likely tell your friend that 'It's a civil matter, not a criminal one!'
All she would have to say is 'Hubby told me to do it' and the authorities would drop it fast.
At least, that has been my experience.
If your friend wants to be shed of this woman and not worry about checking the content of his next meal for poison, or the closet for the wife's boyfriend with a baseball bat, then he should simply go with a divorce!
End of story.
With her past criminal/civil history of abuse, there should be no reason why he shouldn't get custody of the childen....
But that's why I first asked how the wife was with their children, for if the child abuse was long ago and she has been a good mother with their children, your friend might not be able to get sole custody.
Eric The(Reasonable)Hun