By far no expert answers:
1) Because you don't want to suck in/blow around any leaking fuel once you've landed.
2) The filter has a bypass, so a clogg won't flame you out.
As for the angle. There is a marked difference in pitch anyway if you compare a flaps 30 approach with a flaps 40 on a 737. And a 320 landing with flaps 3 instead of flaps full does look rather nose high, but so does any aircraft landing with reduced flaps. My guess: it's a combination of visual illusion due to different fuselage design and flap setting.