Upvote:3
I suggest rethinking this strategy, as you might get into much more serious trouble comparing to where you are now.
First, if you have been convicted for a crime in the US for which you'd be serving jail time, you will be refused admission into Canada altogether. They will check this when you're passing Canadian immigration. This may even be the case when you transit through Canada, as all airports there I've been to (4) work similar to US, where you have to pass the immigration even if you "just transiting". According to Michael Seifert's comment, this seem to be the case with all airports. Then you will be then put on a flight back to US (not the onward one).
Second, once you check in the flight the US authorities would know you're on that flight. While there are no immigration checks on departure, CBP staff routinely patrols the departure gates of many international flights and they do stop some travelers for additional document verification/search. So yes, they can stop you here too.
Finally, if you are caught departing on a one way ticket, there is a good chance you'll end in a much worse situation than you're now.