1. Wrong: Andy hikes as many miles per day if not more than Taylor.
Better: Andy hikes as many miles per day as, if not more than Taylor.
Also better: Andy might hike more miles per day than Taylor.
Explanation: The first comparison uses as needs to be completed logically before the second comparison using than will make sense.
2. Wrong: The Night's Watch do as many pushups per day if not more than the Faith of the Seven.
Better: The Night's Watch do as many pushups per day as, if not more than the Faith of the Seven.
Explanation: Each of the two interrupting comparisons needs its complete and logical second half.
3. Wrong: We ate as little on that hike if not less than the counselors did.
Better: We ate as little on that hike as, if not less than the counselors did.
Explanation: Both comparisons need completion. Without the second as, the sentence implies that We ate as little than would make sense; it doesn't.