Read the HPV/warts article in the link at the top of the STD Forum ("STD Quick Facts and Articles"); and also look at numerous other threads with essentially the same questions. Other excellent sources are the CDC's STD information site (www.cdc.gov/std) and the American Socal Health Association (www.ashastd.org).
You very likely already are infected with HPV-16; if you have a partner with the virus, it is very difficult to avoid. Consistent and correct condom use lowers the risk, but not to zero; with multiple exposures, transmission still should be expected. Indeed, it is possible she caught the virus from you. Getting HPV, including a "high risk" type like HPV-16, is normal; not desirable, but to be expected by most sexually active persons. See the aforementioned article and message threads for more details. To answer your specific questions:
1) HPV-16 rarely causes warts, only asymptomatic infections of the sort your girlfriend has.
2) I can't give you a numerical risk. But if you have had sex more than a few times, I would guess there is at least a 50% chance you have infected.
3) Asymptomatic oral infection may occur; to my knowledge, this has never been studied. But HPV-16 rarely if ever causes symptoms or leads to oral disease of any kind.
4) HPV probably has to be massaged into the skin. But a single episode of condom breakage won't make a signficant difference in the likelihood you have been infected.
5) Yes, the natural course of all HPV infections is that the body's immune system eventually results in regression. It takes an average of about 11 months for HPV-16.
Good luck-- HHH, MD
Read that HPV FAQ that was submitted here a couple of months ago, it has a lot of nice information the other one (link above) doesn't talk about, bye! :)