You underestimate what privacy really is until it's presented to you in a negative way, which this is. I know if some man sent me unwanted, unsolicited naked pictures of himself, I'd delete them immediately. And make him drive. My mother in law failed to inform me about the pics and asked me to delete 2 texts she sent to my wife. Shit, you're a Redditor
So you might want to change the beneficiary to your parents.
Naked photos stolen from cellphone haunt Tampa woman
I hope you find peace of mind soon. Than send the dick pic. I think your wife's mom WANT you guys to part. Not leaving the house, and convincing her to leave sounds like solid advice. You should start building a record with a lawyer, and then proceed. It also seems like she's enjoying the attention from this guy. Even if it means you set up a new living space in the basement.