I was turned back several years ago because of a misdomeaner assault conviction from 1985. The Border Guards were polite but resolute, Do not enter. I had been given probation for the fight and the conviction was to be removed from my record, this didn't happen on the computer they were using. Truly embarassing.
I went through the Houston Consular Office and got a Rehabilition Waiver. Cost $200.00 and took 3 months.
I was told by the Consular Office that when my application was approved my record of conviction would be removed from Canadas database... Not so but it does show me as rehabilitated.
I hope that in time you (the OP) reconsider going back, beautiful country and some of the nicest people I have met in my travels.