Where is the bridge crank that I need? Also, what do I do to get rid of the rock that is blocking my way?

There's a ring called the Divine Sigil, I believe, to melt the rocks in your way. I don't recall where you get either item though. It's been a while since I've been to the Spire. Sorry.

Be sure to check every nook and cranny for chests! I believe you'll find them in a chest. Did you swim upstream near the beginning of the dungeon and meet Kol? Did you go through the Spider area?

+Dr.Pick

This is late, I know. The crank is found in a chest in Kol's vacinity. The Divine Sigil is a ring given you by the Guardian of Earth. (He's also in the Spire.)