This is going to be a bit cold and analytical. I'll let others chime in on the emotional issues in your post.
Do a risk analysis of staying with your primary. The problem is not B (although I agree he is untrustworthy at best.) The problem is that A has not behaved in a trustworthy fashion herself. She is not responsible for the condom break but the rest if her behavior is iffy. If she does not change, are you willing to take the additional risks - health wise, yes but also emotional and financial (long distance relationships are not cheap) - being with her means?
Good luck. You are in a difficult position.