An easy way to kill the dragon is to play on peaceful difficulty before you load your save. The Enderman won't spawn and you don't have to worry about eating food, plus you regenerate health!
Changing the difficulty mid-game doesn't affect trophies.
there is a boosting thread for this game. please do not post boost requests here, as this section is for giving thanks & praises to the author for the guide and to add more helpful tips. speaking of tips, for the Return To Sender trophy, it unlocked for me literally a second and a half after hitting the fireball. the ghast had moved a great deal by the time the fireball reached me, and the return shot was nowhere near any ghast. i have 3 friends that had this happen to them as well, where the trophy pops for just hitting the fireball back. ive also noticed a few youtube videos where this happens as well. i dont know for sure if thats all you hafta do is just hit the fireball for the trophy, but its happened for sure to more than just a couple people
Since the game's update, several things in the Tutorial world have been moved around, including the diamond pickaxe given under the guide for this trophy. It can now be found at the coordinates X:210, Y: 72, Z:93. Hope it helps!