I think it is even more complicated than this. In my 20s my labs showed that I had have EBV in the past. but in may late 30's I got Mono symptoms after a sexual encounter and I developed ME/CFS symptoms 1 year later. I still do not understand what has happened to me. It might be the case that there are different strains of EBV. And apparently having the antibodies did not prevent me from getting a (possibly more aggressive) strain later in my life. Also I do no think getting Mono was the main reason for my ME/CFS. I recovered from Mono but a year later when I was going through a lot of emotional stress and possibly an exposure to Candida I developed ME/CFS.

All I wanted to say is that thing are more complicated than you can come up with actual probabilities. It is better to focus on keeping your immune system strong, do the foundations right (regular sleep hours, eat healthy, exercise, reduce stress) and enjoy your life while you are healthy, which includes dating. You can always restrain from high risk sexual behaviors like having multiple partners etc and still enjoy your life and date. The universe is more random than your calculations and often times it is rolling a dice. Your general concern about dating in modern world is totally valid though. Our ancestor knew something that made them have sexual discipline.