If you disconnect the LAN cable from the modem you can still access the router with a LAN cable from the computer to change the DNS settings. That way you won't download anything while connected to it. When you are finished, disconnect the cable from the computer and reconnect the modem cable.
Sprinkled throughout this very long thread are tips on setting up and getting the most out of Glasswire.
They are cumulative in nature and reposting them would lose the context so I suggest that you start at the beginning and wade your way through.
Post any particular questions you may have and Ill do my best to answer them.
see here: