Two things occur to me:
Putting foam over the top will insulate at night, keeping heat in, just will prevent high heat peaks during the day.
Putting foam over top will prevent oxygen exchange, and in warmer waters this is important.
The foam sheeting doesn't cover the entire pond, just the shallowest edges of the pond so insulation is not an issue IMHO. Same goes for lack of oxygen exchange.
The well option would be an expensive, yet effective way of dealing with it, but well water is low in O2 so you will need to aerate also.
Not difficult to do. Just splashing onto a surface via gravity will go a long ways to increase saturation and blow off any harmful gases. I used to use media filled buckets, but in retrospect believe that was overkill for a 1/10th acre pond. Raceway yes. Pond no.
Otherwise foam during the day, off at night but requires manual labor.
Not necessary to remove during the night IMHO. See above.
A possibility would be to put larger foam sheets suspended a few inches from the surface of the water to keep direct sun off but let air underneath. Evaporation will keep things around the dew point. Perhaps old jugs in the corners of the sheets? Then you have the problem of keeping them in the pond when windy.
Good thinking but IMHO I think you're making it too complicated.