Welcome. This is indeed the right forum. There is no important difference beteween this and the international forum, except for the location of the moderators (US and UK, respectively).
1) There is no single number for condom effectiveness against pregnancy. A woman is fertile only a few days each months; at other times, condoms work 100% of the time. During fertile periods, they probably are around 95-99% effective for any single episode of vaginal sex, assuming the condom indeed is properly used and doesn't break -- perhaps higher if a spermicide also is used, as you suggest in the next question. However, when couples depend entirely on condoms (with or without spermicides) for contraception, on average the rate of pregnancy is reduced by "only" 90%. That figure (called "use effectiveness") reflects the fact that condoms often are not used correctly and sometimes break. Pretty good, but not perfect.
2) HIV infection in women is higher if they regularly use spermicides, because those chemicals damage the vaginal lining. They kill sperm, but they also kill superficial vaginal cells. There probably is little if any increased HIV risk for men, but this hasn't been studied. If the primary intent of condoms is contraception, then a spermicide makes sense, but for STD/HIV prevention, a spermcide is best avoided.
3) All STDs are rare from cunnilingus, both for the oral and vaginal partner. The oral partner in theory can acquire herpes, gonorrhea, or syphilis, but the actual risk is miniscule.
4) Fingering does not transmit any STDs.
Here is another thread that goes into greater detail about condoms and STD/HIV risk:
http://www.medhelp.org/posts/STDs/How-safe-are-condoms-when-used-correctly/show/665887
I hope this helps. Best regards-- HHH, MD