If you want to confront him today just calmly sit him down say
"I know about your affair. So where shall we go from here?"
He might be relieved you know as he was trying to end it and OW was making it difficult
He might say he loves OW and wants to leave you
Do you know what you want out of the exposure?
Do you want to stay with him? If it's an option.
What is your relationship like!
Would he do anything to keep you together? Or is it already rocky?
You might be better talking to the family member who suggested you look for evidence first, get your thoughts in order before talking to H.
If you have children they need to be front and centre of any decisions.
If you don't, depending on length of marriage and assets, if you split you are likely to need to reenter employment. You might want to do that anyway now, are you going to be happy going forward if you do stay together being financially dependent on a husband whom is far from trustworthy?
There are many reasons, outcomes of affairs. There are different approaches to saying you know.
Have a think OP, in an ideal world, what do you want the outcome to be? If it's all in your control, divorce, then that's what's going to happen. If it isn't, H gives up affair partner begs eternal forgiveness, that might not.