Great Post!!!
Even in Commercial fryers used in restaurants the ideal temp is set to 350. As mentioned, do NOT use olive oil!!! It has a much lower burn tolerance and is not suitable for frying. Use a good vegetable or peanut oil. One large misonception is that the oil has to be changed every time you use it. NOT SO! Fryer oil gets "seasoned" every time it is used. When frying chips, fries, etc you can use your oil at least half a dozen times before changing it out. Salt, flour, etc will break down the oil over time and then it needs to be changed. When frying fish you may want to change it out more frequently unless you continue to just fry fish in the oil. Fish will leave that "fishy" flavor on the next item put in the oil. I am sure you have had french fries from Long Johns that tasted like battered cod....
Typically, commercial fryers in restaurants change their oil every 3-4 days and most will filter nightly. So, think how much product gets dropped into an Applebees etc. fryer in an average day. Your 2lbs of fish won't harm the oil. Good luck