1/4 in. x 4 in. Zinc-Plated Toggle Bolt with Round-Head Phillips Drive Screw (10-Piece)

5/16

NO...You get 10 bolts and 10 wings

The direction offer a guideline for the smallest hole possible to insert the toggle, with as little damage as possible to the wall in case you have to remove it at some point. Generally wiggling the toggle spring loaded clasp will fit through the hole snuggly.

I used two and it is holding up 150lbs. But if you have more weight I would suggest also finding and useing a stud also long with useing these bolts.

This brand was...EVERBILT...But they're lots of different brands out there. Just depends on your location on what brands are in your area. But they ALL will do the job that they are intended to do. But if you area is long then I would also use some of the studs within the walls to help in holding the load.

Yes they would...but I would use a more proper length for the job. And I would also add a large washer between the door and rack for extra surface protection so that the wings don't pull through the wooden door.

it will tell you on the package

Yes, these bolts work by squeezing drywall between the head of the bolt and the winged end, creating tension. If the head of the bolt isn't flush against whatever you're attaching to the wall, it will lose tension and fail. It sounds like "EZ Anchor" would work better for your application.

Use an "eye lag toggle bolt" for hanging things from a drywall ceiling. This type of toggle bolt is held in place with tension created from squeezing the drywall sheet between the washer and the winged end of the bolt. The pull-out strength of this bolt is almost irrelevant because the bolt is stronger than the drywall, so the drywall will fail before the bolt does. If you're hanging anything more than a few pounds, attach it directly to the ceiling joists - or span plywood or other material stronger than drywall between the joists and attach to that.