Haha yeah well technically it was the fast idle thermo valve then.. low coolant would result in the FITV staying in full open, and the ECU flipping out because it would read warm but the IACV isn't decreasing the idle.
As for the hesitation, 2 things.. coil and ignitor, or map sensor.. the first being most likely.. there is a third possibility that I won't mention until I see pics of your spark plugs.