I keep the spine on the strop at all times. I used to put slight nicks/wear on my strop at the end of the pull stroke at the very edge of the strop closest to my body. I've never nicked the strop anywhere else save for a miscue at 2AM when I was half asleep and shouldn't have been doing it.
I used to hold the tang between the tip of my thumb and at the first digit of my forefinger and turn my wrist when flipping the razor. When I re-learned the grip and began holding the tang between the tips of my thumb and forefinger and stopped turning my wrist the problem went away. I got that from reading the 1961 barber manual in the SPR Wiki help files
here. The last couple of pages are on stropping properly.