For #1 and #2 I really have no answer. Traffic over Thanksgiving will be a pain. For #3, if you are going to see the falls, the view from the American side is not too great. The good view and all of the tourist stuff is on the Canadian side. So, if your plan is to see this make sure you check out passport requirements. I know that eventually you would be required to get a passport, but I am not sure if it happened yet.
Don t know whether the toll roads would have a website that might give you info on cost, but it s worth a try.I m guessing Thanksgiving holiday may be busy anywhere and traffic is likely to be heavy, depending on when/where you travel.And, as the other poster said, the Canadian side is much nicer [and it won t be Thanksgiving there! - though you still may have tourists from the US] and you will need a passport or passport card or enhanced driver s license to cross the border.