I have offer letters from following colleges in Canada, Centinial, Confederation, Durham and Fanshaw. Which one should I accept?

Yes, universities do take a close look at the number of backlogs. Most of the top good universities do not accept more than 6 (or 8) backlogs. For top universities, it would be max 2. Secondly, they would also look at the CGPA in the last 2 years (4 semesters).

Part time would take time. Compared to other major cities like toronta, Waterloo or Vancouver. But the living cost is less and that makes up for the delay in finding part time.

Your marks should be more than 60% in class 12th and IELTS band 6.0 to 6.5. Marks should not be less than 50% in any subject.

Fanshawe College is an average university. I will recommend you to consider other Canadian institutes. You can consider the Masters in Civil Engineering degree offered by The University of British Columbia, Queen's University and University of Waterloo in Canada.