Canadian Tax Implications of US Startup Shares Vesting

Hello, I'm joining a startup as one of the first couple of hires. Initially as an IC, but then as an employee, once global payroll is set up. I'm a Canadian citizen, resident in Canada, and working remotely. The company is a US corporation.

I'm trying to figure out my Canadian tax liability on the equity I'm receiving. This is restricted stock purchase award to purchase common stock, with a 1 year vesting cliff, and the remainder vesting fully over 4 years.

I've been advised by a CPA familiar with US/Canadian tax that I fill out the 83(b) election for the IRS, but that the stocks will be treated as regular income at FMV, when they vest. This is concerning to me, depending on how FMV is calculated.

We just closed a seed round, which implicitly values the company. If we raise again in the next couple of years, is that new valuation the FMV for the shares vesting after that point, even though they're completely illiquid? That's what scares me. I don't want to be on the hook for 100's of k in tax for something that I can't generate any actual income from.