Immigration can refuse the address if it is clear that the PR will not be staying at the address when the PR card arrives in the mail.
What you should have done in that case would have been to follow the instructions of CIC at https://services3.cic.gc.ca/ecas/?app=coanotify&lang=en&_ga=1.114876993.734650769.1340054404 and provide your friends address again that the immigration officer had refused. This has worked for many people whose address was refused.
You should have applied for your SIN too while you were still in Canada as it only takes a few minutes.
Your problem now as you have identified is that you can not apply for a SIN using only your COPR once it is more than 1 year since your landing, see http://www.esdc.gc.ca/en/reports/sin/apply.page
Your other problem is that as a new PR, you should have provided an address for your PR card to be mailed to within 180 days. Not having done that, you will now have to apply for a PR card as if it was a renewal. This is not a big deal. You have to fill out a form, see http://www.cic.gc.ca/english/information/pr-card/apply-how.asp and you need new photos and there is a small fee. However, the processing time will be for that of a renewal which is currently 151 days and not the processing time of a new card which is currently 45 days.
This means that in your SIN dilemma, if you do not either apply by mail or go to Canada yourself to do it before one year has passed from your landing, you will have to wait until after you have arrived in Canada again and until after you have applied for your PR cards and have waited 5 months to get them. You can not work in Canada without a SIN so you will be living off your savings.
Also keep in mind that you should apply for the PR travel documents now in order to make sure you get them before you want to leave because the processing time for them can be long as well. They are usually valid for 6 months so you can apply now even if you don't plan to go right away.