I actually was going to ask the gear question myself...
I was told never to tie the car down while in gear, stress on the components, but once the car is situated, put it in gear, that much more safety from it rolling off the trailer...As for the number of straps, I am one for safety, so the more tie downs the better, but the safety chain I use will be plenty, the car will NOT break that chain, but it is easy enough to take on and off.
Alan