I had to take Easy To Read, because it was a prerequisite of Smooth Lover.
I hadn't looked at the STD rules yet (though I did take Disease Resistance x2, because it fit), but they seem very disjointed, and need some proofreading. For example, it says to roll 1d20 to determine frequency and severity, but the given ranges are only from 1 to 8, so I think you'd roll a d8 instead. It also needs cleaning up regarding curing the disease naturally, and if you can cure a chronic disease non-naturally, and what the DC to do either of them is...
For the diseases themselves...BMS? Tuna? Mummy Crotch Rot? Overall, they seem to be much more for comedy than as a sex deterrent, though I guess that's fitting.
There appear to be 3 DC's. The first is to see if your partner has an STD (1d20 vs. Settlement Size+Social Class Modifier). The second is to see if you contract the disease from them - Constitution check (not a Fortitude save) DC of 2+Disease Mod+1/2 rounds of sex. The most contagious is +4 (gonorrhea, syphilus, STLycanthropy), so with a +14, Jakk would have to go for 18 minutes before being at risk of infection.
The 3rd DC would apparently be the roll to recover from a disease...but it doesn't appear to be explained.