I once had to sue an employer for wrongful dismissal over anonymous social media posts I didn't even write when I was in my early 20s in Canada and won a small settlement. Process took about 3 months but it was worth it. My lawyer told me most companies, even gigantic ones (i sued a large global airline) are extremely cheap, they have house counsel they use for everything and rarely seek out specialist lawyers which means that their lawyer(s) will be absolutely trounced by your employment specialist lawyer during every settlement meeting. It was amusing watching the highly arrogant Toronto lawyer that was parachuted in, with no experience in employment law, bungle and flounder around failing at every turn during settlement conferences with a judge.

You can refuse overtime in Canada unless you signed some work contract that says you agree to work overtime, ergo you need a real employment lawyer to go over your case. A real employment lawyer is somebody attached to an actual firm specializing in employment law and not the first search results in google, which if you check their name will also be the 'experts' in injury law, a bunch of other spam ads. All you need is a half hour call with them and possibly emailing them your work contract documentation if any exists. Of course they will tell you to start documenting everything like the rest of the comments here suggest.

As for planning an escape if your market is bad then recruiters have an even worse time, so find one and get them to help you. Establish yourself in remote freelance outfits like TopTal, CleverTech, or even Salesforce who hire all over Canada. Then ask your employment lawyer what to do, don't just quit maybe you need to file harassment paperwork first or bait them into firing you by refusing overtime.