I'll bet that a rumor that a woman has HIV is a strong indication that she does not. Or at least that someone is being vindictive, without evidence.
In any case, very few women in the US are HIV positive, except injection drug users, commercial sex workers, or the wives or regular partners of HIV infected men--and not most of them. Most important, a negative HIV antibody test a month after exposure is highly reassuring. For still more security, have another test after 6-8 weeks have gone by. You can be sure the result will be negative.
So the answers to your questions are: 1) Almost zero. 2) Half way condom slippage doesn't matter; for HIV, it's as good as complete coverage. 3) See above. You really didn't need testing at all except for reassurance; and that's the only reason to consider repeat testing. It's up to you.
Good luck-- HHH, MD
I saw this site giving details. From that, it seems an average of only 10, 000 women are reported positive every year in USA. Of this roughly 65% acquired the disease through heterosexual contact and the rest from drug use.
http://www.avert.org/womstata.htm
http://www.avert.org/statsum.htm
And even those statistics overstate the number of infected women to whom most forum users might be exposed. Most are the wives or other regular partners of HIV infected men and are not "out there" dating or having commercial sex.