1:Firstly, how does the whole free to play work? does it basically mean half xp and credits like 90% of other free to plays..
Might as well sub, so many restrictions that you basically either sub or quit through anger and frustration.
2:Also if i was to sub, i was a sith marauder, but found anh got nurffed a bit so changed to carnage before that got nurffed lol. is sith marauder still a useful character to play?
Yep, just become a Smash junky.
3: I was level 50 something, before quit, if i was to resub would i be able to even get into any groups or even survive pvp as i hated PvP before i left due to people running around in silly armor where you couldn't damage them, basically meant no chance for casual players to play in PvP.....how are things atm?
Yes, so long as you do regulars. Just grind warzones to get Conq gear.