I'm a big believer in intel, but really, what do you need anymore for? You already know your wife is having an affair.
I think your efforts would be better spent on learning to set -- and enforce -- boundaries, and on two books that I would recommend: No More Mr. Nice Guy
Hold onto your N.U.T.S.
As a third, possibly Co-Dependent No More.
What are the current financial arrangements between you and your wife -- who pays for what?