I am not aware of any research, or even informal reports, about STD risk from oral exposure to urine ("watersports"). Whatever risk there is probably is very small, for all STDs and probably zero for HIV. The greater risk is for enteric infections, like salmonella or other gastrointestinal infections, if your commercial partner happens to be infected.
As for cunnilingus itself, the only available data are for gonorrhea, and those results showed that in people attending STD clinics and tested for gonorrhea of all potentially exposed sites, gonorrhea of the throat is very rare in heterosexual men, with no difference in those who have and have not performed cunnilingus recently. Chlamydia is uncommon in the mouth and throat and probably rarely if ever acquired by cunnilingus; if anything, probably even lower risk than gonorrhea. To my knowledge, nobody with HIV has ever reported performance of cunnilingus as their only potential route of exposure. Logically, oral herpes and HPV are possible, but no data are available. But since you already are infected with HSV-2, you're immune to catching it again, so that's really not an issue. Hepatitis is not a realistic concern. Syphilis clearly is possible, but is too rare in most settings (in the US) to be a significant considerration.
All in all, therefore, your risk is probably zero for HIV and very low for other STDs.
Good luck-- HHH, MD