Canadian with Canadian Employer working in USA

[icefisher]

Hi, I've searched the forums and haven't found anything quite the same as this, so please link me if this has already been answered:

I am a Canadian citizen. My spouse is a US citizen. I work but she does not and she has no income (recent past, present, or near future).

Until Oct 1, 2019 I was employed by a US employer in the USA (under TN). On Oct 1 both my wife and I moved back to Canada, and are now living there with no residential ties to the USA. I am now employed and paid (salary) by a Canadian company however about 75% of my work for the rest of the year will be performed while physically present in the USA (under TN). Future years are expected to be similar 75% workload. If I file as a dual status for 2019 in the USA, my calculations show that I will owe considerably more taxes due to not being able to claim a personal deduction (x2) and the requirement to file single for the full year. As I understand, I have the option to file as a resident for the full year due to having an American spouse.

Below are my questions:

1) Do I need to elect to file as a resident via my spouse or does the Substantial Presence Test leave me as a resident for the full year anyway (unless I make a closer connection election)?
2) If I file in the USA as a full-year resident do I pay taxes to the CRA for Oct 1-Dec 31 and deduct from my US taxes, or the other way around?
3) After Dec 31, if I am no longer a US tax resident (rescind election or never make election), should I be paying US taxes for the portion of time I am in the USA? If so, how do I calculate which days I owe US tax, especially days where I am paid to travel between countries?

Thank you.

[nelsona]

Since your spouse is a US citizen, you certainly can file a 1040 joint with her to benefit from all the normal deductions, exemptions etc.