Look like short of water. Perhaps because large plant in a small pot?
How often do you water? And how do you decide to do so?
Same questions about fertilizer.
What's the weather been like?

I've been watering every day unless the soil looks obviously wet. Fertilizing never happens (since I don't know what to use), and the weather's been cold for tomatoes at night - the low this week is 34 degrees.

The plants are inside now, and the German Queen is pretty much completely dead - the tomato's the greenest part, all the leaves are wilted and/or yellow, and she's bent in half where I'd fixed a break earlier in the year. Mr. Stripey still stands a chance, though. I'm planning on using a grow light over the winter to see if I can keep her going until spring.

Honestly I wouldn't make the effort to try to keep it growing. Your choice of course but not only is your zone an issue for winter-growing but relatively complex conditions for indoor growing are also needed.

Add to that it is a heavily stressed plant already and has been nutrient deprived for some time apparently so is both root bound and anemic in appearance, the odds of any cuttings from it being healthy are slim to none.

Better to spend the winter months learning more about proper container growing methods rather than spending time and money on trying to salvage this one.

Dave