Q1, 2- If you are breatfeeding, make sure you drink a LOT the day before the flight and during the flight to keep up your milk volume. As mentioned below, you will want to feed during take off, landing, and for comfort so maybe more than usual. Bring anything that you would normally use to soothe your baby, like a blanket, swaddler, pacifier, iPod or other music player with large headphones that you can place next to baby's head at low volume, pillows to put under your arm to make feeding more comfortable. If you are comfortable with it, some infant Tylenol to help with sore ears if needed. My super duper secret tricks that totally make me a bad mommy- 1- a mini bottle of maple syrup, put a little drop on your finger and put that in baby's mouth if there is a complete meltdown and 2- If you have 1 drink, like a glass of wine, and nurse the baby, that might help you both relax! LLL says it's OK :)
On a lot of international flights they have airplane "cribs," kind of like little pack n plays that hang on the wall between sections. They only have a couple, so ask the flight attendant before you even get on the plane and they may be able to hook you up. In general, the flight attendants are your allies- they want your baby happy as much as you do! Do not be afraid to ask for anything that they can help you with. I have heard that a hot, damp paper towel placed at the bottom of a cup, cup placed over baby's ear can help equalize the pressure. A flight attendant could help you with that, and may know other tricks.
Q3- If you and baby are both US citizens, you should bring passports for both of you and a certified copy of baby's birth certificate and immunization records, plus any medical records for you or baby that you might need in an emergency for either of you. You should also bring something that has emergency contact information for someone on both ends of the trip.