1: Make sure you DLC is working properly. I.e, make sure the "Turn Vita Chambers On/Off" option is in your options, if it isn't, you will need to re-download it from another account on the same xbox. Related thread.
2: Start the game on easy, and turn the Vita chambers off. If you use one, it will ruin that playthrough for getting Brass Balls. Obviously, get to the very end of the game.
3: Save before the final boss battle. Then, beat him like normal up to the final Adam taking
. When you walk up to him and get the option to "Press A", this is where the trick comes in.
-Immediatly after pressing A, press start.
-Go to the options, and head down to the difficulty.
-Press left to change it to Hard, then press start
to get out of the menu, not B.
-Watch the movie, and as it starts the non-ingame movie you should get the achievements.
I just did this about 10mins ago, you can look at my account to see, so it still works.