There should be no "Theories" On early access, as that was done with 1.0. You get to play a few days earlier than everyone who bought the normal edition if you have the CE.
You can use your 1.0 character during the Early Access, you will be able to use your 1.0 Character on ps3 since it will be linked to the account you logged into.
You do not need to buy the PC version again if you already owned 1.0, you will be able to download the client for free and if you had the 1.0 CE you will also get early access for free on top of the month free, On top of the week of open beta if you choose to play it (it carries over into retail so basically it would be like round 1 of early access for most players with a small break afterwards).
1.0 Legacy Characters are limited to legacy servers for a small period of time until the newbie servers catch up to having a lot of 50's (I would say a couple months being that there will be people at level 50 within the first few days to a week I am sure).
If a newbie signs up they can choose any server, Including legacy. I Know a lot of people who will join legacy servers as newbies just because they want experienced people to play with, but the general consensus is that most people dont want to play legacy because they are jealous of the bonuses 1.0 characters get (so say the whiners on the beta boards any way). Heck, they are even claiming to try to kick people from parties in duty finder if they find out they are legacy players, I have even seen people start setting up "Legacy Free" Free companies and linkshells. Its getting pretty lame haha.