If you go to the library section of this website, you will find several technical bulletins and manuals from around the time this beautiful refrigerator was built. The exact year may not be there, however I don't recollect such massive changes in that time-period that one which is a bit older or newer won't hit the problems.

The butter warmer was a rolling disaster and not having a working one is no loss. Personally, I'd do what my parents did: Disconnect the dratted thing at the wiring block and be done with it. However, if it matters to you, there are references to it's many, many problems in the literature stretching through the late 1960's.

The problem you are having with a too cold crisper section can be caused by a number of things and people here who know more than I do will no doubt be along - there's also extensive problem/solution lists in the Frigidaire tech support literature.

However:

1) The cold control (the thermostat) may be faulty. I bought one for our '67 Frigidaire not too long ago, they do show up on Ebay and it is possible to configure a generic to work.

2) If anything has gone wrong with the defrost system (and careful, here, Frigidaire used non-standard color coding on their refrigerator wiring, including 'green/yellow'and 'green' caring current!) it could lead to this, too.

That's covered extensively in the tech support bulletins, too. Not difficult, though.

3) If a drain is stopped up or a 'flowing cold' fan is broken it can cause these problems, as can a jammed vent door. I'd start there.

These are very robust units - we have a 1967 which is working great - and their main problem was plugged up drains, frozen flowing-cold fans (replacements are still available) and failed defrost timers. 

the super-heat setup sure looks like two separate units. Frigidaire did a lot right on these refrigerators and they are always worth repairing. Pity so many service in-duh-viduals will pretend a simple, generic part isn't available or lie that there is a 'freon leak' and no other coolant will work.

I am [ unfortunately ] very familiar with this ref. It has two evaporators, one under the floor of the freezer section to cool the freezer and one behind the back wall that cools the ref section.

There are two evaporator fans, one in each section, the freezer fan runs whenever the compressor runs, the cold control only affects the freezer temperature, it causes the compressor to turn on and off to maintain proper freezing temperatures.

There is a thermostat behind the ref section breaker strip that controls operation of the ref section evaporator fan, this thromostat turns the fan on and off maintain proper ref temps.

The likley problem with your ref is the sealed system is weak and it is running too much of the time to maintain 0F in the freezer, when this happens the ref  section thromostat cycles the fan off when the main part of the ref is cooled to say 35-38 F range. Then the compressor is still running and the evaporator behind the wall is getting colder and colder and this extreme cold air is counter convecting and causing things in the bottom of the ref section to freeze.

There is no easy fix for this problem, we had this model in a beautiful all porclean cabinet model and we tried everything for several years to get it to work correctly. Finally I pushed off the back of the truck at the scrap yard.

I can think of a few creative ways to fix this but none are easy.

Note FD only used this system on their early FP models, they wisely abandoned this system around 1964, so FD FP refs after this time do not have this problem, although I have seen almost none from the later 60s that are working correctly. They are usually not cold enough in the freezer and too cold in the ref section, and are running almost all the time sucking up lots of power, Our webmaster Robert just gave up on his beautiful Turquoise FD ref and said his power went down $28 a month.

In general vintage FF refs are hard to keep running correctly as they age, the best ones are WP built models and GE refs with hot-gas drfrost

I was wrong, this model does have two evaporators. Good to know!

We had a 1965 Signature frost proof top mount for a brief period when I was a kid, and it behaved much like John described above.  It had a single cold control and stuff would freeze in the fresh food section while the actual freezer was never cold enough. 

I agree with John's statement that Whirlpool and GE refrigerators from this period are far more reliable than the problematic Frigidaires.

It seems odd to me that both your account and Jon's indicate over-cooling at the low end of the cold control.  I mean, why have B, C, 1, 2 and 3 if A is overkill?  Seems like a cold control issue when viewed from that particular angle.

Then there's the issue with that poor beleaguered compressor running almost constantly.  As John L. suggested, the compressor could be getting weak.  But again, the cold control could be the cause, calling for cooling when it's already cold enough in both sections. 

John L.'s mention of the refrigerator section's thermostatically controlled evaporator fan seems to implicate the thermostat, which may be causing the fan to run more than it should, and lowering the fridge section temperature as a result.

I would like to think the compressor isn't the issue, but it may be soon if things continue as they are.  If it is, that's the most costly thing to fix -- and good luck finding anyone who would do the job.   I'd try addressing the other potential trouble spots first.  A universal fit cold control might not be as difficult to find as that specialty thermostat, but this seems like an air flow problem -- too much of it in the fridge section -- that may be the result of a bad fan thermostat, so that is where you might want to start first.

Keven already provided a link to the literature library, but here's another one for Frigidaire refrigerator-freezers. 

There's an 88-page 1962 service manual available to download for $7.99.  I'm sure it will provide part numbers.  There's also a 53-page Component Diagnosis manual from 1973 for $5.  I don't know how generalized it is or if it would cover models dating back to 1962.

Sounds like the cold control has issues.  Who knows?  It might just be a loose wire.

My aunt's new Frigidaire of similar vintage had that "instant ice" system.  I was very jealous of that, and her entire fridge, as our fridge was a drab '49 Westinghouse single door that would be with us as a daily driver for about ten more years before it finally became a garage fridge.

$80 seems a little steep, even for NIB, but I'd still be tempted.