Do not reveal to your h that you have informationon the affair. Keep your information/knowledge to yourself. Never tip your hand and give up what you know to him.
As for aging...yep...they all do for a while. They are burning the candle at both ends and can't do it. The depression and guilt are what drives the crisis and it takes a very serious toll on them for a very long time. If he's starting to look bad, he'll begin complaining of being sick/aches and pains, etc.
Do what you need to do to protect yourself financially.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
