For 1, 2, and maybe 3; often people talking about 83(b) will have the ability to early exercise; that is to exercise the options before they vest. If you leave before vesting, the company has the opportunity (but not the obligation, unless mentioned in the contract) to buy the shares back for the exercise price.

My questions would be are these options qualified ISOs for US stock purposes or are they NQSO or something else.

If they're ISOs and you can't early exercise, then when the first vest date comes, you need to know the FMV at that day to consider your options. You wouldn't need to file an 83b on vested options that you exercise though; there's no election to be made, your holding date is the date of exercise and you'd have income for alternative minimum tax on the discount at that point; the type and amount of income for regular income tax would be determined when you dispose of the shares. Consider the holding requirements for a qualifying disposition of ISO shares; if you don't think you'll meet those, it makes more sense to wait and not exercise until you're ready to sell (or the options are likely to expire, if they're in the money)

On 4, I don't know anything about Canadian taxes; it will make a difference if you work within the US or within Canada, but if you work in the US as a US person, I wouldn't expect any Canadian taxes to be due; but I wouldn't trust me, I'm just a random internet person.