How would I go mathematically paying my lender his loan back per month?

In mathematical terms it is basically an optimization problem - where is the optimium ROI as you are moving all the other parameters.

Is BRRRR method feasible (or mathematically worth doing) in Vancouver region?

It will be difficult to answer the question without the mathematical numbers.

Sure, mathematically you will be able to exceed a 12.00% yield, but IRL there will be down time between transactions, so your actual returns will be less.This scenario also assumes you do not have to foreclose. 

From a mathematical standpoint, I know leveraging to the hilt is better than purchasing with cash (unless of course, you lose the properties in a downturn as so many did in 2008..).

@Francis DinhFrom a purely mathematical point of view as demo'd in my spreadsheets, this is not a disaster.

Taking a brief look at the website of FlashCMA (I'm sure the others are similar), one line specifically says this:  "FlashCMA performs a series of common sense mathematical adjustments automatically and then allows you as a Real Estate Professional to make any other remaining adjustments." 

If we were playing Jeopardy, the answer would be:  "What is the power of compounding, in a mathematical equation"?

In an extremely general non mathematical sense, you're kind of asking, do you want 10 properties in 15 years, or 20 properties in 30 years.