Hi, Rusty here,
I would scrap this hide and start fresh. The way I learned to make rawhide came from a Bruce Grant article. The process
Started with stretching the hide first, then dehairing. I had problems when the hide wasn't dried long enough( 4 days were best for me), the same rotten spots showed when trying to dehaired.
More time stretched and left to dry was best and I got a better hide to play with. Cutting the long strip after and stretching for a few days as well, gave some really nice strings for different projects. Keys: stretching, scraping and drying adequately, then dehairing before cutting I to a long strip to stretch and dry some more. 'Twill be a long winter of braiding! Have fun!!!