You are common-law spouse once you have live together for 12 months. You do not have to continue to live together during the application to "maintain your common-law relationship".
You will have very unconventional proof of cohabitation but you do have proof from the application to your company to live together by requesting "companion linked" and you physically moved into his room.
You can get life insurance regardless of your age (it's actually cheaper to start young) and make each other the beneficiary. You can ask coworkers, common friends and if your supervisors know write letter about your relationship. Do you have shared finances? Joint bank accounts? (I think he can be added to your account in Canada and create this joint account)
As much as you think it's hard to proof common-law, it's harder for you to qualify as conjugal. There is no legal barrier. He is from a visa exempted country and marriage is possible. Since you are already going through the Procedural Fairness step, be prepared that your application will likely be rejected.
Have he look into getting working holiday visa in Canada? He can work up to 6 months and stay up to 12 months in Canada.
http://www.cic.gc.ca/english/work/iec/eligibility.asp?country=it&cat=wh&#country_category_name
You can also consider doing a court wedding or a small wedding. Since you two are committed anyway, it may be a natural step.