after you get chainsaw,reload lvl St. Crux Cemetery , push on D-pad to right to select chainsaw, then go through the lvl. At first hole you must go down to get the Key. Then go to right. when you will come to big vertical wall,change the weapon to sickle's and with them you not get trouble to run up the wall. But be carefull there are many enemy's. Quick push LB to use magic, and fast push d-pad to right to change weapons to chainsaw again (RB botton to change from the sword).
Then it's easy to finish the lvl.
P.S. sorry for my bad eng ^^