1) Green tea is best brewed with water at the temperature of the "first boil". That is about 180 F, well below the rolling boiling point (212F). In other words, when boiling water for green tea, the kettle should not be left unattended anyway, but caught before it comes to a rolling boil.
Another thought is that there are plenty of nice stainless whistling tea kettles on the market. Yes, they will have heated the water to 212 by the time you hear the whistle, but at least they haven't boiled dry.
A coffee maker can also be used to heat water for tea. The water has generally cooled a bit before it hits the tea, so it's a good choice - as long as the coffee maker is very clean. Traces of coffee make tea taste horrible. You could get a small 4 cup Mr. Coffee style coffee maker and dedicate that to tea making. These have a 2 hour shut off and generally run about $20 at most stores.
Zojirushi sells a wonderful water dispenser that allows you to choose the water temp (the Japanese are very particular about their tea, you know). Unfortunately it's about $100, but probably worth it.
Re: the discolored stainless. Yes, this can be sanded/scoured off and then the surface can be brought back to a high polish. It's just surface discoloration. My favorite cooking pot has a nice purple sheen to the outside from one of my mishaps - I've never bothered to remove it; doesn't really bother me. I did have to scour the interior to remove whatever it was that I burned into it. Fortunately it's a very well made pot and it didn't delaminate or warp from the high heat (a gas stove probably helped there as well - electrics are more likely to be warping pots and pans).
Professional metal finishers use a stationary buffing wheel (looks like a grinder) and various grades of "rouge" (mild abrasives) to bring the metal surface back to a shiny mirror like finish. I don't think I have the patience for that, but I have gradually brought scratched metal parts back to a satin finish.
You might look up metal shops in your area and take the pots in to them for color/debris removal and polishing. Get an estimate to see if it would be the same or cheaper to just buy a new pot.