I can’t talk to the others but I do know a bit about AIDS. Before I share the following I should say I am not a doctor or any kind of expert. I briefly dated a researcher who was looking at the spread of HIV.
The specific issue with HIV as I understand it is that blood to blood contact is very much more likely to lead to transmission. This is why unprotected anal sex, with the associated risk of tissue tearing and bleeding, is extremely risky and unprotected vaginal sex also carries significant (but much lower) risk. The Virus is present in semen (lower contractions) and other body fluids. Saliva and gastric juices kill the virus so there is little or no risk from oral sex.
Dinosaurs like me remembe4 the three groups who first saw the spread of aids were intravenous drug users, gays who practiced anal sex and people who used infected blood products. I heard it said that if you were heterosexual, did not inject drugs or use blood products, and were not a sex worker and your partner was also not in those categories, you were more likely to drown in the bath than contract aids.
The messages around safe sex are very conservative. Personally I believe there is quite a lot of morality dressed as science in this area activiely prosecuted by the medical profession. But this said, I use a condom.