I can't remember the level's name, I think it's the one right before the castle, but there's a level with a door that has the royal seal on it...it's an outdoor level, with broken catapults lying about...sand golems and mantraps are the monsters wandering about. Anyhoo, since you've been to the church, you're now able to open that door. Inside that chamber is the card that you use on the castle gate's force field.
As for the four statues, after you turn them all, you'll notice they're all looking at a general location at the left wall ("left" as in, when you first enter the church, the wall on your left). Just run along that wall, and you'll automatically trigger a switch that raises a section of the wall, which leads to a little treasure chamber.