To answer a few more of your questions.....
when I flew with Gulliver, I did have his collar with his ID tags on him at all times and did the harness and leash when he was out of the carrier.
i did the same thing you did and sent a blanket to the breeder a couple of weeks before I picked him up so it smelled like me when it arrived and like his family there when left. He flew with the blanket in the carrier with him.
His breeder sent a bag of food and a couple of bully sticks with him so I had that in my 2nd carryon. Check with your breeder to see if they're sending food or anything else along with your new baby. If they're not and it's going to be a long day with the flight and waiting beforehand, find out what he/she's feeding and bring a little ziplock bag of it with you. Don't forget a little fold up travel bowl or bring along one of those water bottles with the attached bowls that you can pick up at Petco/Petsmart. You can fill it with bottled water once you get through security
Once you book your flight online, make sure you call the airline and let them know you're going to have a pet on the return trip so they can get that on record. You'll pay the pet fee at the gate when you check in, but it's important to get confirmation for the pet well ahead of time.
we played for quite a while before we boarded so that he was tired and my guy is VERY used to travelling so I didn't have or plan to use any kind of calming aid.
harness, collars and leashes......collars are for the bling. ID tag, rabies tag, etc. Leashes should only be attached to a harness, never to the collar. Type of harness is going to be personal preference. I use a lot of vests and dresses (i've got a girl too
) with D rings on them and I love them. I also use just basic harnesses that you can pick up at any pet store. There are several sellers on this site that make vests and harnesses if you want something nicer also. I use cat collars on my babies because they have the breakaway in case they get caught on something.