I’m not going to tell you WHAT to do. Consider the long term.
My FIL stayed out or rather was left out of almost everything when my sitch went down.
Me and FIL were always relatively close during the relationship.
Now, we almost never talk. Haven’t messaged or spoke to him in almost a years time. Except for saying merry Christmas.

Me: 34
Stbxw: 30
D:5 D:3
Mini bd: May/June 2019
Married: Aug 2019
BD: 6th Dec 2019
OM Confirmed: Feb 2020
March 2020: I filed for D
Waiting for D to be finalized and W to move out end of January 2021