Unfortunately, as bad as your wife is, I don't think your situation falls under the abuse category. If you look at your own Appendix D, being slapped, choked, isolated from family, confined to your house, forcing you to take drugs, etc. These are VERY serious things involving force. In your case, all your ex did was just cheat on you and smoke weed (didn't even force you to do it).
I know this isn't a relationship advice forum, but seriously bro, you gotta man up, take your licks, and move on with your life. Everyone on this board agrees there's not much you can do if the marriage breaks down, to keep your PR, aside from trying to live a lie and dealing with a cheating wife until your Condition 51 expires.
You said you came from the US, why are you so worried about possibly being deported to there? It's about as identical to Canada as any other country in the world in terms of culture, prosperity, etc. I think instead of worrying about your PR, you should divorce your wife, return to the US, rent a nice place, find a job, and maybe date again. You don't even need to marry since you said so, you could just date casually, lots of women aren't interested in marriage. And because you've presumably lived in the US for a long time, when you go back there, it's where you are most familiar, and it shouldn't be too hard to pick up the pieces again.