Julie. Your H could be the exception. Or, your H could be like mine, and the EA caused him so much guilt that he just reacted with anger towards me because he couldn't justify his own behavior. Even when confronted with the evidence and admitting to the EA, he still said in the same breath that "she has nothing to do with this."
In my sitch, the EA could have been a PA and I will never know unless he admits it. Everyone who I have talked to tells me I am kidding myself and it was a PA.
In your sitch there could be either an EA or a PA and you will never know unless he admits it. Or like I said, maybe your H is the exception. Yes, his words and behaviors fit the script, but there are exceptions to every rule. People can be angry for a lot of reasons.
Julie, don't react. Don't take a lover. If you end up divorced there will be lots of opportunities for lovers and you will be guilt free at that point and emotionally available to pursue such a relationship. In the meantime you are married, and your behavior is about you and your morals, not a reaction to H.