Maybe hearing him finally admit to things under oath will end up being validating/vindicating/cathartic?
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.
