Then I read that without solid intel there's no point in exposing the A. I just feel trapped in no man's land...thanks for talking me down.
Not really accurate.
Without good intel, you still have two viable options:
1) Expose by bluffing: "I know all about you and so-and-so, and this isn't working for me. I won't live in an open marriage." Remember, she STILL doesn't know what you know, and what you DON'T know, and her finding your voice recorder makes HER incredibly nervous (even paranoid) about what you already have -- not the other way around! YOU know that she found it right away, but how does SHE know that? How does she know you don't have three weeks' worth of damning recordings already, safely offloaded to a CD somewhere and put away safe? How does SHE know that you don't have PI intel on her? Pictures? Etc.??
She doesn't.
2) You can just ASSUME she is cheating on you, and act accordingly.
I'm as pro-intel as anybody, but your hand is FAR from empty if you don't have it. I think you pretty much know what's going on here . . . don't you?
I go back to what I told you the other day, that went uncommented on here: If she's NOT cheating on you, what was she doing checking her car for listening devices???