Actually just got back from Japan on Tues. Will post a TR shorty. In terms of the dateline, I actually asked a Shayla about it (from the Chabad of Kobe when I got there, didn't know it was an issue until I got on the plane)
Anyways I left on Sunday of last week in the AM, in terms of davening and tallis and tefillin, I met someone on the plane who told me that you daven once on the way there and twice on the way back. That didn't sit well with me 100% since if I made a mistake then I would miss the opportunity for tefillin.
basically, the flight took off at around 8am Sunday and landed Monday afternoon at around 2pm. I davened before I took off, and a second time (since it was another day) when I landed at NRT.
it's kind of interesting, even though it didn't get 100% dark during the flight. But I was told that the idea of it not getting dark doesn't really make a difference because your still crossing the date line, and it is a new day.
On the way back, we left at around 7:30pm Tuesday (davened earlier that morning) and we arrived in JFK at 6:30pm on Tuesday, so didn't have any issues that way.This was kind of spur of the moment thinking since I didn't realize that it actually was a shayla before I left. Obviously ask your LOR for all halachic q's.