I have reason to believe my crazy ex gf has an audio bug in my home somewhere.
I doubt it. Might be too much TV. As was stated, bugs are short range. Since they have to be small, they don't have enough battery power to transmit long distances for very long.
If it's a telephone bug, then just don't use the telephone for a while and see if things resolve.
If it's an app on your phone or something on your computer, you'll need help figuring that out.
Legal issues aside, of course.
As for crazy ex girlfriend, well, there's worse stuff that can happen. What makes you think she's bugged your home?
I need help on which of these bug detectors are best suited for this case.
Bug Detectors
Don't waste your money. If it's an RF bug, the battery will run out soon. If she has access to your home to replace it, change the locks.
Distance yourself from her, and if you think there's a credible threat, make sure you get it documented and a restraining order. If you did find a bug, you'd be hard pressed to prove it was her.