I don't think shutting the aerators off for 4 hr during the heat of the day will make much difference in pond water temp. Definitely keep them running at night.
Instead of $10K running electric, what about a diesel or propane generator?
The fish slowing down eating tell you that they are stressed, either by water temp, O2 levels or both. The spawn up here is just winding down too, so that could be another reason why you are not seeing them, but if they were feeding great 1-2 weeks ago then forget I said that.
Surface agitators (either a paddlewheel or volcano) combined with bottom diffusion aeration is the only way to maximize O2 levels in a pond that is over 8' deep.
