One thing I DID use social media for was to indirectly communicate with my WW a couple times. For instance, one of the things I was promised in our D was the toaster oven. I really liked it. Well, she KEPT it!!!! Now, I know how this game works... 1) she was being a jerk 2) it gave her an excuse to contact me later for a temp check. As predicted she messaged me one day out of the blue and said she had my toaster oven and she wanted to get it to me.
At this point I was 100% NC. I didn't even want to reply "NO!" to her. I did not reply. Instead, I bought the most expensive toaster oven I could find and made a great post about cooking an awesome breakfast with my new toaster oven. Lulz. I would find out later that my message was delivered loud and clear.
Ask your L about taxes. We agreed to simply split the refund 50/50. She tried to say she deserved more because XYZ, blah blah. But did agree to get halfsies eventually.
As far as notifying him about the money, I say no. Just use it for what it is intended for and keep a record of it all in a spreadsheet. If he asks about it, simply respond "Yes, I received it."
I can feel that you want to pursue sooooooooooooooooooo bad. Please resist the temptation. I only leads to suffering.
Save yourself. Nobody is coming! BD:11/2017 Filed:12/2017 Final: 2/2018