[1] All of that 198 permissions are per unique Google domain. Google currently has 198 localized & regional domains, see here: https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1mXWo6uco/wiki/List_of_Google_domains.html , far better than granted permissions for "access all websites" which many extension do.
[2] This extension updated since January of 2019, if abuse happen in this extension, it probably get reported and get removed long time ago. And Firefox store probably blacklist the author and affect my other extensions too. So, no, nothing wrong.
[3] If you know Javascript coding, you can type about:profiles in url bar to know "Root Directory", then navigate your "Extensions" folder inside that root directory in file explorer. You can uninstall and reinstall the addons in this extension page and sort by date in file explorer to find out which .xpi file(latest file after reinstall) is related to this extension. Copy that .xpi extension file as backup, then rename .xpi to .zip, unzip it. You can see javascript plain text inside and its manifest.json file which listed all the google domains permission.