Hey Alex,

It sounds like you have tried all of the main fixes for water damage. Unfortunately, since the dock connector and battery replacement did not fix your problem, it is highly likely that the water caused a short on the logic board, effectively frying it. Did you happen to notice any burn marks on the logic board while you were inside it? You can open the device back up and check to make sure that you reattached all of the connectors correctly, but in the end it sounds like you will have to replace the logic board.

Before doing so, you might as well take it into an Apple Store and seeing if they will replace it for free. It is a long shot, but I have had some luck on them replacing a water-damaged device before.

Hope this helps. Good luck!