Equipment fouls

[Bullycon]

RichMSN's reply to my mouthpiece story got me thinking a little more about equipment-related fouls and how little I understood them. So I've summarized my understanding of them below. Does anyone see anything wrong below?

There are three fouls that can be called regarding player equipment:
1) Failure to wear required equipment during a down. (1-5-6)
2) Failure to wear required equipment just before the snap. (3-6-2d)
3) Failure of the head coach to have his players wear required equipment. (9-8-1h, referencing 1-5-2, 1-5-3, 1-5-5)

So, what circumstances call for each foul? A few scenarios, with my assumed rulings:

A: Official observes player without a mouthpiece as the ball is about to be snapped.
Kill play and administer 5-yard penalty for delay?

B: Official observes player without a mouthpiece an instant after the ball is snapped.
5 yards, live-ball, succeeding spot? (Or kill the play immediately and penalize for delay?)

C: Official observes an unbuckled chin strap halfway into play.
No foul, since it cannot be assumed it has been this way since the snap?

D: Official observes a player as he unbuckles his chin strap during the down.
5 yards, succeeding spot?

E: Official observes a player as the down ends who has the bottom of his jersey tied into a knot.
15 yards, succeeding spot, charged to head coach?

F: Official observes a player with a knot-like jersey as the ball is about to be snapped.
Delay? Or 15 yard USC? Kill it before the snap in either case.

G:From an actual youth scrimmage this year:
As the team breaks the huddle, the coach points out one of his players and says, "He lost his mouthpiece, is he OK?" I said, "No, he cannot play without a mouthpiece." They replaced him and the game continued.

Assume the coach doesn't speak to me, a play is run, and after the play, I notice the kid does not have a mouthpiece. The coach then says, "He lost it on the previous play." 15 yard USC here? The coach just admitted he let a player play knowing he was missing required equipment.