Having recently spent 6 hours in an airport departure lounge with a 17 month old because of a flight delayed by 5 hours, I would never choose a flight with transfers unless it was absolutely unavoidable - because of hand luggage restrictions, once you have the toddler basics (food, bottles if you use them, nappies, etc) there's precious little room for toys, and departure lounges are not toddler friendly (there wasn't even baby changing facilities in the one we were stuck in). Baby bottles are useful even if you don't use them, because the security people let you take them and their contents (ie suitable water/formula/other drink) provided you taste it - just pour it into a cup when you need to give it to your dd.
On most airlines, you don't have/can't buy a seat for a child under 2, which means having your dd on your lap for the entire flight. Check with the airline whether they will let you take the car seat on (and get it in writing from them if they say you can take it in the cabin). If you do take a car seat in the cabin you will probably have to pay for a seat for your dd.
I can't suggest answers to your other questions, but I would suggst taking more food, drink and nappies for your dd than you think you will need, because you never know if you will need it. Bear in mind that depending on where you are going, it could take a significant amount of time to clear immigration and collect your baggage, so you need to factor food etc for that as well.
I was advised to give my dd a bottle when they the plane is coming in to land - it worked for us: she kept pulling at her ears, but the action of sucking eased the discomfort. A dummy would probably help too, if your dd has one. And don't put the travel disc things on your bottles - the pressurization makes the discs leak more than the bottle without a disc leaks.
Dd has only flown within Europe - I'm dreading when we decide it's time to take her to see MIL and PIL in California