If your partner hasn't been tested and you have any doubts, non-microwaveable plastic wrap is better than a rubber dam.
As long as his "rash" is not painful and your vagina is not causing you any major discomfort, I wouldn't worry.
BV is a broad category that includes yeast overgrowths, the most common problem for modern vaginas due to the amount of sugar consumed.
The recommended approach for oral sex is to use a dental dam.
Food is my medicine and loving what I do is my best vaccine.
The decision of not using condoms and dental dams is an individual choice once you have birth control in place.
Honesty is always the best policy but you can have sex with herpes and not pass it on.
STIs happen and there's no reason to feel shame or deny yourself pleasure.
You are in no danger of contacting STD's from your nipples touching a man's penis except maybe Herpes.