TravelAuthority

Best website: Bing.com/travel - the fare predictor is pure genius. Not even Delta agents have access to that information. A close second would be Skyscanner.

In general you want to book 6 weeks to 12 weeks in advance. Any earlier and the flights won't be on sale, any later and the others will have already snapped up all the low fares. Award tickets are another animal though.

I'd look for flights outside of ATL. Unfortunately you're in a Delta hub and that means they have very little competition. You might try flying from a smaller city too. Sometimes booking from Columbus, GA or a city close to ATL will give you a much lower fare even though that flight actually connects in ATL anyway.

Try Skyscanner. You can also send me a message with the dates, places etc. and I'll look into it for you. BTW, I don't get commission or anything.

But $1,100 is about average for a summer round trip to Europe.

A doctor on my flight to Japan got upgraded mid-flight for helping out. that's not an official policy but I've seen nice flight attendants do it.

Yes, after your flight you should call or email (preferably the later) and let them know about every single thing you didn't enjoy about your flight (food, movie selection, rude flight attendant, tray table didn't work, wifi didn't work etc). The airlines have a specific department to deal with complaints and they'll give you tens of thousands of miles, free business lounge passes, travel vouchers, drink tickets etc.

Go with Economy Comfort or Exit Row. That may cost you a bit though. Also take a look on Seatguru.com to determine with seats have the most leg room. Unethically, you could call the reservations agents and say you have a medical disability that requires a bulkhead seat (you don't have to state exactly what it is and Delta agents are forbidden to ask).