The hardest part of this section (really, the whole game) is the stone angle gate. The strategy I found for this section was to stay all the way against the back gate. Use the slime blower to keep the tombstones off Ray. When Ray is clear, shoot the tether at a skull on the gate first and then shoot an angel.
The boss fights are much easier. The trick is to destroy the pillars Shandor uses to recharge.