Below, lower, under, above, over

Would someone please kindly tell me which prepositions are correct and how to choose between them?

When you have a fever take a bath 3 degrees below/lower than/under your body temperature of 37 degrees.

I usually take a bath 3 to 4 degrees higher/above/over my body temperature.

Oral and axillary temperatures average about .5 F to 1.0 F (.3 C to .6 C) degrees below/lower than rectal, ear, and temporal readings.

Oral and axillary temperatures are on average about .5 F to 1.0 F (.3 C to .6 C) degrees below/lower than rectal, ear, and temporal readings.

If you are trying to sell property over/under/above/below market value....

If you drive under/below 50 mph, you are fine.
If you drive over/above 50 mph, you might get into an accident.

Thank you