That’s quite a number 
. Is the Web GUI still responsive?
Yeah, you can run multiple instances no problem (other than higher resource usage, obviously). You just need to use different ports for the GUI, listen addresses (see https://docs.syncthing.net/users/config#listen-addresses), and local announcements (see https://docs.syncthing.net/users/config#config-option-options.localannounceport and https://docs.syncthing.net/users/config#config-option-options.localannouncemcaddr).