I also agree- the A in my sitch has been going on for months- I truly know nothing, but at the same time know everything. I have busted every lie (almost) in the past month. But it's exhausting and frustrating when SO does not fess up.
Puppy's right- the benefit of the A in my sitch is that I know it has more to do w/ her than me. It's still difficult and a blow to the self-esteem, but hang in there...
It's good your asking about ways to blow the A. I blew my W's A to OM's girlfriend. Now we e-mail eachother almost daily. You do need to be careful, and don't expect to have them suddenly come clean- possibly quite the opposite. Don't give away your source of intel, and be ready for hell afterwards...