Yes you are correct.
Line 4 would be the basic personal amount for that year since he didn't have any income entering zero is fine.
Line 6 would be zero
Doing adjustments to previous years (back to 2008) might not be necessary. If you have indicated on the DTC application that you wanted all the previous years included, CRA will process those adjustments for you.
It would be beneficial for you to also create if you haven't a CRA "MY Account". https://www.canada.ca/en/revenue-agency/services/e-services/e-services-individuals/account-individua...
