No, it was simply regrown. The damage was done and the power was removed as a result.
No, he refused initially because of Fandral's hubris and insult at the War of the Shifting Sands. The second time around when Alexstrasza and Ysera were there to bless Teldrassil he was lost in the timelines trying to find himself going evil as Murozond.Moreover, Ysera and Alexstraza both blessed Teldrassil, however, Nozdormu flat out refused because of the way the Night Elves were. (Too much pride in who the were as a people.)
They will never get a paladin class and neither will the Zandalari since Rezan is dead. If you want a paladin humans and blood elves are there for you or something with hooves.Need to be open to the possibility that Blizzard has been setting Night Elves up for some sort of Paladin-esque class. I secretly hope the Zandalari are going to receive the same treatment. Sick of Femme Elves and Holy Cows.