geez, Nick--you're making my brain SMOKE!! Great questions. Bet Jumper can clear up some or all.
Pretty sure # 3 is moot--point to point should be NYC base--don't forget EWR!! (many of us wish we could...)
I think the respective websites for DL and NWA will show who operates which one as codeshare or not--which zed works for what metal?
arghhhhh---too many G's!! Pull out, pull out!!