Here's an update on the fishing-line fence and peppermint oil: My fishing-line fence is about 5 feet tall and apparently not high enough. My trailcam caught a deer inside the fence and I found a single tomato plant topped. All the lines - about five of them - are still intact. This morning, when I checked the camera card, another deer was inside but no further damage. Nothing has touched (or eaten) the young melon seedlings or pumpkin plants. Yet.
I am not going to spray the plants with the peppermint oil anymore, because when I did it the first time, I thought I had killed them all. Leaves were brown overnight. The good news is that they were not killed and have begun to produce new growth.
Going to try some store-bought repellent left over from another season and crossing my fingers.