1. No, you cut them, so they are not reusable.
2. That part is confusing as hell. But all you have to do is cut off the bottom 2 rivets and the bolt directly above that on the fender lining.
Then you pop the 2 or was it 3 reusable clips above the grille, and the 4 on the very bottom of the bumper.
3. Look at Step 4 on the PDF. It's located on the bottom of ea corner of the liner/bumper.
The scary put is pulling on the bumper to separate the clips/snaps. I was afraid of breaking the bumper.
Do like the video by pulling the plastic fender guard halfway around. It just snaps into place.
Where your bolt was, there's a lip there, so you kinda pull back a little bit to clear the bumper from that mounting point. Then you just pull and you'll feel/see the bumper popping off. You keep working it all the way underneath the headlights too.
Do the same thing to the top of the grille. That top black piece is snapped into place also.
Concerning the rivet size, I don't know exactly. I haven't used one yet. I've been driving for the past several days without the rivets in place. I knew I had to go back in, so I just left them out for the time being.
Hand Riveter with 40 Industrial Strength Poly Rivets