How can I prevent "Reset network settings" on my iPhone from affecting my Laptop?
Check to seen if your passwords still exist under Safari &gt; Preferences &gt; Passwords on your Mac. Maybe they are still there.

If this doesn't work, try the following: Unplug your router's ethernet cable (so that iCloud cannot sync with the server) and try to restore your from Time Machine. This should revert your Key Chain. I recommend disconnecting your router because if you just turn off your wifi, it will probably turn back on after the restore is done and sync with iCloud again.