I saw this post last night and wanted to think a little. This stuff is confusing to me to but here is my best thoughts. FLA Full Load Amps I think means just that. With the motor (no pump attached) loaded to it's maximum rating that will be the current draw. Now, when the motor is hooked to a pump and moving water is the motor putting out its max power? No. What is the real load? Depends on how much water you're moving which is the amount of work being done. I think the 16.4 part of the info is what I said. It makes sense the 4.4 is the low speed amps.

Now this stuff I do know and is back to basic electricity. From copper wire tables at 77 deg F. a 100' 12 gauge cord will have a resistance of 0.324 ohms. (#12 copper is 1.62 ohms per 1000 feet and you have 200 feet of wire). At 16.4 amps that is a 5.3 volt drop. Fairly significant. Starting current will be a lot higher momentarily. The 15 amp breaker will probably get warm so you should consider going to a lower resistance line and a higher rating on the breaker.

Hope this helps.
Al