I am a US citizen. My wife lives in Canada 7 months a year. What do I use for "exchange rate" and also "Pension Income exempt under a tax treaty".

The Bank of Canada US annual exchange rate is 1.2986. Any CDN source pension would not be exempt in Canada. US social Security payments have a tax treaty exemption as follows:

https://turbotax.intuit.ca/tips/reporting-american-social-security-income-in-canada-6220