Where does he go when he lands in toronto?
If he has the PR card and his passport he goes to self service kiosk where they scan the PR card and print out a receipt. This receipt is given to a CBSA officer, best case scenario they dont ask anything and let him. Otherwise they might ask basic questions like how long you been outside the country. Where does he work?
Do they need anything else besides his pr card and passport?
No he doesnt need anything else besides his pr card and passport. Just to be sure, have him carry his CORP as well.
Does he need to fill out a customs card even if he doesnt bring back new purchased items?
He might have to, but its not a big deal.
Also when he lands and presents his pr card will the officer know how long hes been outside canada???
They might not ask because the self service kiosk is supposed to make life easier PR and citizens. If they do ask, he can mention he is coming here for good. As long as they feel he intends to stay in canada this time for good, there will be no issue. The issue comes when they suspect the person doesnt intend to stay in Canada