Hi,
1. I dont think you will need to include your parents details if you are not sponsoring them. I marked the sheet as N/A as i was not sponsoring them.
2. I am not sure if its better to get married first and then apply for your permanant residence but if your partner is sponsering you should be married or be qualified as conjugal partner. See this link it will help you a lot.
http://www.cic.gc.ca/english/immigrate/sponsor/spouse-apply-who.asp3. As long as you are an adult (16+ years, legal age to marry in UK) you can get married.
cheers!