#1
not blink 182 or green day, but like bad brains or 'Came without warning' by Scream

also not metallica because it's metallica drumming.
#3
Songs like that are just about speed and stamina really.

Metal can be like that too.

But punk can also be hard.

But metal can also be easy.

Also not metallica because it's metallica drumming.

Does that help?
#5
Depends on the standard of the musicians you are talking about. Don't think it's that much to do with genre. Although certain genres will have certain precedents of standard. Historically, punk was technically easy to play. These days, it's much more varied.
#7
As one who has drummed for both, it depends. If you can groove or just count to 4, doom metal is easy. So is thrash.
Things requiring various blast beats and constant doubles or intricate kick patterns ups the difficulty.

Punk is generally easy. Simple beats. Until you start playing faster d-beat styles, or some of their fusion generas like blackened crust. Banewreaker is a good example of more intricate drumming. But they are so far removed from the usual punk sound.