On buses, personally if they start at 3:30 I wouldn't get out there any earlier than 3:30 maybe head out at 3:15 at the earlies, but I don't want to just be standing waiting. Corrals aren't even open right away so even if you are on the first bus you'll still have to wait before walking to the corral so if you are later you can still get to the front of your corral as long as you are there when they open the corrals.
For training I would get to as fast you can, sure you can get by on 14-15 min/mile, but if something comes up and slows you down (unforeseen crowding, pain, stomach issues, etc.) it's nice to have the buffer of banking time if you can. So, taking the time to train now is important and if you can get faster go for it and if you can't at least you tried. With 6 months to go you can get some great training in to cut that time some maybe.
As for the expo if there is merch you must have then you probably should go as early as you can on opening day. Seems like you never can tell if stuff will run out. Darkside ran out of a lot of stuff it seems, where Princess was a nut house at first but was being restocked. So, if it's must haves then go early.
Funny on watching the Amazing Race, I watch it too but DVR it for when I get home, I prefer watching movies that will make me sleepy and TAR never puts me to sleep it's too exciting.