Vivaldi with vertical tabs work well for this too, coupled with the keyboard shortcut to bring up a fuzzy tab selector. It's pretty awesome. Plus you get tab cycling in recently used order - the only sane option.
It costs a few bucks but BeyondCompare http://www.scootersoftware.com/ is the best differ I've used. It's not terminal based, but is supported on Windows, Mac, and Linux.
You could - but it would need to be every 1 minute. Google tears down your app after 60-90 seconds of inactivity.
Some folks have resorted to pinging every minute but Google discourages that since it ties up their resources. If everyone pinged their site once a minute then resources would never be freed....