The bad thermostat experience I had with my '57 GE Combination was the reverse of what Ken described above. The fridge was not cycling off, the layer of frost on the serpentine evaporator coil (on the ceiling of the fridge section -- I think Hotpoints may have located their version of this on the rear wall) was thicker than I'd ever seen it, and the temperature in the fridge section was approaching freezing. Even though the cold controls on mid to late '50s GEs are notorious for failing, I don't think that's your problem.
I tend to agree that the trouble is likely the result of a failure in the sealed system -- the compressor in particular. You shouldn't have to set the cold control to 9 for optimum temperature in both sections. That's a red flag for sealed system issues. If the fridge is running more often in an attempt to maintain proper temperatures and instead of developing frost in the freezer it's just sweating, that's another indicator that it's struggling.
Is the fridge making more noise than it used to? That's a common indicator that the sealed system is compromised. Quite often a failing compressor is not only noisy, but hot to the touch. That's something you can check yourself -- it's about the size of a 3# coffee can and easy to spot under the fridge at the rear.
You should probably start looking for a vintage replacement fridge ASAP, as the behavior you've described sounds terminal. It might be best to snag a cheap or free fridge off of craigslist to hold you over until you find another vintage one, as your Hotpoint is probably only going to become less viable, and likely sooner as opposed to later. :-(
