I am sorry about your wh's horrible allegations. How hurting and painful it must be for you!
Do you have a lawyer? If you do, you could bring up this incident and ask for legal opinion. You could just put this on record and not act on it. Just to protect yourself.
And then like what SH and surfer have suggested, step away from this. These are the crazy rumblings of a very lost and disturbed man who feels cornered. Do what you must to protect yourself and then put yourself out of the way of the impending car crash.
Cherry, my views here will be controversial. Have you talked to your mil about validation? I don't know how possible it is for her to adopt the condemn the sin but not the sinner stance towards wh. Your wh seems to be trying to win your mil over with more extreme measures the more she sides with you.
Btw, I don't condone any of your wh's actions. And I do think that he's a big selfish jerk and asshat. But this big selfish jerk comes off as desperate and lost.
You can call me Dory/ Grl.
As a wise fish once sang,"Just keep swimming!"
It's no use to go back to yesterday because I was a different person then.