Values look good, and calculations match your expectations. I like R12 (bot not 10K, something like 330 or 1,000) only because it provides a bit of isolation from the gate. But Charlie is right, it probably makes little difference. Best way is to go ahead and try it, and then optimize as needed.

As far as the N-ch FET, not sure this would work for this application as the turn-voltage for a "bad" condition would be the same as the ADC voltage for the "good" condition.