everybody here is right!! what i would add:
1. in ur letter explaining ur intent of return to Canada explain also ur current ties with the current country of residence; make them see that there are not that many (no family, friends) and the main thing which holds u there is ur partner - once he can go from there, there is no reason for u to stay; by the way, if u stay in the current country with tourist visas CIC does not consider that u reside outside Canada
2. if u still have Canadian bank accounts, credit cards is very good and it's another proof that u have never intended to leave Canada permanently; also maybe u have membership cards (to gyms, libraries, colleges) those could help too if they r not expired
3. if u visited Canada often (maybe some family or friends) while u were residing outside, tell them - it's not a significant proof but it's still good
4. the most important for them to see is that u will have a the place to stay; if u have family or friends who could help u with that for the first months there and also write support letter saying that they will, then i don't think u need to lease with so much time before (u never know how long this process could take)
overall many people are in ur situation and they have been approved as sponsors maybe even with less proof so don't worry; but be prepared that before they issue the PR visa for ur partner they will ask clear proof that u (the sponsor) will leave the current country
of residence (resigning ur current job, canceling ur current residence visa or other depending on the region)...but until then, there's still long way...good luck
