I understand condoms reduce risk of hpv 70% for one exposure. what's the baseline risk? "new hpv is rare beyond age 30-40, and unlikely to cause disease or symptoms in newly infected men or their partners" - can a number be put to "unlikely?"

About half of all people acquire genital HPV by the time they have had 3 separate sex partners, and the numbers go up from there. Most infections are acquired by age 30-35; beyond that age new exposures are increasingly unlikely. At your age the chance of a serious health outcome (e.g. penile cancer) from new HPV is extremely low. That risk is primarily from HPV infections acquired long ago.