Making the bridge fall down is very easy. You do not need to throw it across the gap at the metal tower holding the bridge up (near the Idol Door). All you have to do is grab a bomb (which is on the bottom of that spiral staircase near the door) and go into the room. Then, (still carrying the bomb) go to the metal tower that is directly in front of you. Place it there. Then go left to where the broken chandelier still lies. There are 2 candles still lit. With the wooden stick, press circle near the candle and your wooden stick will be lit. Then go near the bomb and the fuse will be lit. Stay away from the blast. Then, you'll watch the bridge fall down so it's crooked.

** Did you drop the chandelier on the bridge first? If not here's how to do it: from near the saving couch, go through that open door (don't go downstairs at all) and go to the other side of the room (follow along the sides, don't go on the bridge or you'll have to jump and if you miss, you'll die) and look at the windows. You'll notice you can jump on them. So climb all the way to the top where there are wooden planks suspending the chandelier in the middle of the room. Then, go near the edge and let yourself drop down. Then the chandelier will drop and break. Then you'll have those two candles ready to be light the bomb on fire **

Okay, back to where the bridge is crooked. Leave this room (you're still on the bottom level with the crack in the room) and go up those spiral stairs into the room and you'll notice the bridge is down so you and Yorda can open the Idol Doors. So...get Yorda now and lead her down the now broken bridge. Watch out, Shadowdemons are waiting for you, so (my opinion) just make sure you have her hand and run straight for the door! Then, she'll do that bright lightening thing and all the Shadowdemons are destroyed and the door is open. Congrats you did it! haha

Hope this helped! I got stuck at that part too! haha

When you get the bomb, head back out and to the left. When you get to the area with the torches, light your stick, light the bomb, and throw it at the tower thats on the left-ish side of the screen.