Hi - I'm new to this forum, and apologize if there is already an answer out there but I couldn't find it...

I've flow 10+ times internationally with DL buddy passes and always had a great experience, but haven't in a couple of years. Now I find myself once again with a pass and, and while I understand the etiquette, rules, and dress code, find myself with other questions.

(I realize that the friend issuing my pass can answer a lot of these questions, but out of courtesy to my friends very gracious mom I'm trying to get some answers on my own so I don't have to bother her with a lot of back and forth.)

Part 1:

-- Is it true that there is now a $50 per leg fee?
-- And a fuel surcharge?
-- Is there a equation I can use? i.e.: 10% of the highest Y fare + 20% tax + fuel surcharge (which I know is always in flux)

Part 2:

-- I'd like to fly ATL > DOH, but it doesn't look like there are straight up DL flights....just wanted to confirm that nothing has changed in the code share arena.
-- Is it true that I can do a days-long layover? e.g.: SIN > NRT - spend a week in Tokyo then continue on NRT > ATL?

Any responses are appreciated as I'm trying to book ASAP, so starts the second leg of my year-long travel adventure! Many thanks and happy travels!