Beyond offering support I'll add--and this may apply particularly to you kas since you've worked in roles related to the court--some LBS imagine/idealize "under oath" means telling the truth. This is a legal matter. Expect him to admit to that which you can prove, and forget that which you can't prove. Expect to learn more details, but don't expect him to come clean.
He doesn't know how or when I found out. S21 walked in on them but left before anyone saw him. I imagine he will saying something dumb like yes he's dating but it wasn't until after he left me which sounds all peachy keen except I had to file for divorce and he has been stalling for 2 years. It got so bad that the judge awarded me legal fees for the delays.
