American wife Canadian husband living apart

I am assuming you mean "dependent" and not exemption as now with the increased standard deduction there are no additional credits for "exemptions", so to speak. If you are noticing an increase ("uptick") in your taxes due this year thus far due to selecting MFS, try going back and selecting MFJ to see if it balances you out. In selecting MFS, you are only getting the $12,400 for your standard deduction as if you were a single filer versus MFJ your standard deduction would be $24,800. Huge difference. If all else is the same as last year with your situation tax-wise, you are clearly far better off with selecting MFJ. 

Per IRS (and TurboTax, for that matter), if your spouse is a NR Alien, you can treat your spouse as a resident alien for tax purposes.