Yes, you will have to get over sharing your relationship with complete strangers, we all do

Unfortunately it is a necessary evil. It's best to have a nice cross-section of evidence: photos, emails, phone records, proof of living together or visits, cards or letters (either to each other or from others to both of you) chat records, joint accounts/credit cards, joint purchases, declaring one another as beneficiary, proof of wedding ceremony and/or trips together. Etc. Be creative

You don't have to send it ALL, but just make sure you send a nice complete picture of your relationship. Just think "if someone looked at this pile of evidence, would they know that we are a genuine couple, who have known each other for x amount of time, who really love each other and plan on a future together?" If the answer is yes, you're good to go

EDIT: also, don't underestimate the value of including things that show that you know each other's families. Social ties as a couple are important. You should give OP2 a readthrough, it'll give you the right idea.
http://www.cic.gc.ca/english/resources/manuals/op/op02-eng.pdf