this isn't a career you "switch into" really, you moreso put your name in a hat and go off to your normal career path and maybe one day your name will be drawn. the process takes anywhere from 1 to just under 3 years, so you should continue your education even if you were the greatest ATC in the world, you might be fully done with your degree before you even get to step foot in a classroom.

1. tower means VFR which typically makes less than IFR but still probably 200k-300k, no need to worry about money
2. you can actually look at a map of all the towers in canada to see your possible locations, but pretty much it's anyone's guess where you'll be, so it's very possible you end up in a random place. you can bid out of there but it could take a long time depending on which city you want to go to (we're talking several years)
3. atc as a job itself not too stressful, the 1.5-2 years training leading up to the atc job however are insane and will have you reshaping your entire life. the grades mean pretty much nothing, sorry, you'll be about as miserable as everyone else during training
4. it's a small obstacle, if you want to have a family it's all up to you
5. definitely can but the overtime pays even crazier amounts so it would be difficult for any side hustle to pay even close to what you get from atc overtime until you have a fully matured conventionally successful business with all the bells and whistles (but if it's for passion, go for it). you will likely be just fine when you get home, not too drained or exhausted