hi tink23,
if u have Canadian credit card maybe it's good to show that too
also maybe u have some friends in Canada who work in similar field as u, past employers and they could write u a letter describing ur capabilities, experience, how well u worked together and saying they would recommend u to their company or if they have good network they would include u in those networks to get a job faster; even the people from ur past summer job; at the end it does not matter what kind of job it is, the important is to show u have the minimum to support both financially
also u could start applying already; it shows them that u started searching for a while, maybe u'll even have some interviews when u go back (more proof to show with the application)
the letter from ur parents it's very good; us too, we'll be living with my parents when this is over, my name is also on their lease, i don't know if it makes any difference; some people had this letter notarized, it could b better
don't worry as soon as u arrive in Canada I'm sure u'll find a job while his application is in process and u can update the information

all this is an ongoing process; i don't think u need to wait until u find a job
good luck!
PS: u know that u can sponsor him while living with him outside Canada, right? (and wait for the process together) yeah it would b a little more proof to show (re-establishment to Canada etc but for me it's worth the effort)