Welcome to the forum.
This was a low risk exposure, since a) assuming neither of your threesome has special HIV risks (e.g., injection drug use), it is unlikely either of them has HIV; b) heterosexually transmitted HIV remains rare in the US; and c) you used a condom. Neither BV nor IBS would have any effect on the test results or on your risk for HIV.
Most important, your HIV test results are conclusive: no matter how high or low the risk might have been, the tests show you were not infected. Below is a link to a thread that goes into detail (and links to another thread as well) about HIV test reliability. As you will see, it isn't necessary to wait 3 months for conclusive results, depsite the official advice from most health agencies.
http://www.medhelp.org/posts/show/1891685
To your specific questions:
1,3) This was an extremely low risk exposure with regard to HIV. I would put the chance at no higher than 1 in many million.
2) It doesn't matter whether, or how long, HIV can survive in the air. Your test results show you were not infected.
4) Yes, your results are conclusive.
So all is well -- no worries! I hope my comments have been helpful. Best wishes-- HHH, MD