You shouldn't have a problem driving a rental as long as the rental agreement is in your name and the vehicle is insured for Canada.
You're likely going to have to pay tax on the new TV since it isn't on your original list.
I don't have an answer to your towing question, but here's where you can download a PDF of the Driver's Handbook for planning, securing and checking cargo loads.
http://www.ccmta.ca/english/pdf/cargo_driver_handbook.pdf