As a start, let me tell you that genital warts is not something serious. It is more like a skin disease just that happens on genitals. Most of the cases will not bring any health problems.
You had so far did everything correctly, going to pap smears and got treated in December 2011. And the latest check up was done in May 2012. Almost 6 months after the treatment. It's difficult to tell whether the warts will come back again. Some experts' opinions think that 3 months after treatment, without warts appearance again, it is considered as treated. Some experts think 6 months. So, I would say, yes you are pretty much in the clear.
To your questions:
1. You would not know. The fact is you should continue to do annual pap smears. If no abnormalities found in the pap smears, you are fine. If very unlikely found, get treated. And, I do think 2 years is a reasonable time to eradicate HPV from your body.
2. Yes. In fact, I would like to think you have already eradicate HPV from your body. Even if HPV still exist, they will not likely to pose a risk to your health anymore, probably will not causing genital warts anymore.
3. Cervarix vaccine is to protect against the HPV strains that cause cervical cancer. It does not protect against all strains of HPV. You have got the vaccine, which is actually the right thing to do.
Now, finally, you do not have to avoid sex at all because of the fear of HPV transmission. Practice sex safe. In almost everyone that is active sexually, has HPV or will have HPV sometime in their lives. Some HPV causes genital warts, some just causes nothing. Over time, they will be eradicated from the body. So, it is a fair bet, that your partner or future partner already have HPV.
Here, I attach a link from STDs Expert Forum answered by Dr. Handsfield, which you can refer: