Sunday morning should not be a busy time for US preclearance at YYZ T3 (DL). Two hours should be OK. The reason why all the US bound flight are posted as three hours is that it could take that long at busy times: Mon am and Thurs/Fri pm.

There is no Skyclub for DL US bound passengers. Intl passenger use KL Crown room. All DL TATL flight out of YYZ are code shared with KL/AF.

Sky Priority is for DL Gold or above or SkyTeam Elite + (KL equivalent); so plan on extra time for checking in.

DL YYZ DTW flights are all CRJ regional jets which has smaller carry-on space than larger planes. If you have a large carry-on be prepared to gate-check it.