Are Russian schools better than Canadian schools academically?

By "schools" do you mean "universities" or actual schools as in primary, secondary or high? The word "school"only refers to the latter in Russia. 

If you are talking about schools then probably yes, they are more...rigorous. At least when it comes to STEM subjects. All school education culminates with the Unified State Exam, so you can look that up and see example papers for yourself. 

Universities...well...similarly to schools the curriculum is probably more demanding in theory. That is, in top engineering universities like the Bauman university maths and physics curriculum is very hard. In less prestigious schools though, where the students are much dumber and less motivated, you could easily "pass" subjects with very little studying.

in the old days, there were elite schools in Russia for the academically gifted and party officials' children.  I can see that those would be more challenging.

Russian schools are very demanding. But so is IB. You're weak, but your family is uncooperative in providing a suitable environment for studying, and your stepmother is belittling & undermining you. Use noise-cancelling headphones to shut out the noise. And let your stepmother (& your father) know that belittling your efforts is counterproductive. It's not as if stepmom knows diddly about requirements for IB diplomas or serious careers & planning/preparing for them.

"Better" is a very vague word. It depends on what you think the purpose of learning is. Her school may have required great deals of memorization, and the teachers were harder on the kids in terms of emotional support. Even in the early 2000s, schools in the former USSR countries used the approach of embarrassing students by announcing their grades publicly (I know this from one person who studied in the US and changed her university when she went back to her country.) BUT memorized facts are not what people need going into the future. You can Google those. What you need is to be able to read and comprehend information, analyze it, and apply it. That takes a good deal more mental processing, and arguably more mature intellectual abilities. 

in the old days, there were elite schools in Russia for the academically gifted and party officials' children.  I can see that those would be more challenging.

No it is not better in Russia than it is in Canada.

Why would you be weak because IB classes are stressing you? 

Can you study elsewhere? School, library? Even a friends house?  Get some noise cancelling head phones