I'm not an expert on form, but I'll do my best to answer 3 and 4.
3.) Grip width is completely up to you based on what you feel is your strongest grip and the one that feels most comfortable for you. A lot of times (not always), raw benchers will usually have a somewhat "close" grip. Watch some videos of raw lifters benching like Jim Wendler. Most shirted lifters will go for a grip that is as wide as allowed during meets, both because of the nature of a shirt/path of a shirted bench, and the fact that it cuts down your bench stroke.
4.) Basically whenever people are talking about tucking your feet and arching to bench, they will say "drive your heels into the floor"...what they mean is get your toes into the ground and push forcefully to use your legs to drive the bench and stay tight, but aren't actually saying that you need to get your heels onto the ground.