I'd keep that backup & put it aside. IDK if you upgrade fr the v4.7.x firmware series but if you did v.4.8.x is a serious departure 'under the hood' in the way GL handles key components (eg: dnsmasq). See below.
Regardless I'd nuke & reflash v.4.8.2 as if it was that very firmware that came straight out of the box. Using the 'U-boot WebGUI de-brick' method will ensure no traces of any prior firmware files. That tarball backup you have is just a collection of UTF-8/LF text files. I wouldn't dare try uploading in an attempt to restore but the contents of those text files are easy enough to extract whatever relevant portions you need to get back into shape. Then make a new 'known good' backup.
TL;DR: kill it with fire.