1 & 2. That doesn't apply in my game. There's just the word "Donate", and if you click on it, there's the "money transfer" sound. Nowhere is there any way to control how much you give. But I'm pretty sure that different temples take different amounts, and if you donate often enough the party is endowed with different benefits.
3. You and I must have different versions of the game. I know mine is the unmodified v1.0, and the only ship to EIW leaves from the dock on the island north of Silver Cove town on a Thursday – IIRC it's called "Barracuda". I can't remember off-hand which island in EIW it docks at, though.