First time tower - multiple questions

After my calculations, my plan was to put everything I can in the trailer. Exceptions would be a small cooler for snacks/drinks and small backpacks for the kids (tablets, kindles, some books, small toys).

My Durango manual just says I need a WDH for anything more than 5,000lbs - but nothing about hooking it up.

I will look at some of those mirror suggestions.

Good advice on the electronic brake...