This immigration process requires sacrifice and life is all about taking risks. Everyone seems to have an opinion but you should consult with a lawyer. Everyone's situation is different. You were also a minor too.
If you miss your interview, you will be refused. I don't think the IO questions your status in the US or how you came. That comes in when determining where your application has to be processed. At the interview, you are proving that your relationship is genuine. That's it! Make sure you have additional documentation addressing that.
On a positive note, you may not be called for an interview.
Just out of curiousity---->Did you use your Guyanese address or your U.S. address when you filed your application?
http://www.canadavisa.com/canada-immigration-discussion-board/-t87102.0.html
Take a look at this thread. Maybe you can get some help. Just a brief: SaraLune's husband tried to enter the US illegally and was caught. It showed up on his FBI record but he still got through. It is different from your situation but a bit similar.
However, the fact that you entered on someone's passport and visa, you may have to do an fbi clearance on their name as well as yours and submit an explanation when submitting your paperwork to CIC....IDK. I'm only assuming here.
Maybe you can ask this question on a new thread: Are you inadmissable to Canada for using someone's passport and visa to enter the U.S.? Explain your situation. Try to address this question to top members like PMM, Leon, Scylla, Rejessome, and Qorax.