It's about a 10.5 hour flight, nonstop from LAX-CDG.
It's about an hour more going the other direction. Wish the night flight were the longer one!
Yes, you can avoid this. One example is flying Aer Lingus and preclearing in Dublin before your US arrival.
I've only seen prescreening in Toronto (I understand there are a few Canadian airports). I hope other European cities adopt this! That would be great! I flew out of CDG, LHR and FRA and none of those have this feature. Does Aer Lingus fly to the west coast non-stop?