shop refrigerator operation

Maytag 21 CF refer with freezer on top wasnt cooling beer enough so I started to investigate. Was cranked up,refer to max and freezer to max with no effect, seemed to be stuck at 50F in the bottom refer portion. I cleaned the lower coils (dusty) and the top coils were lightly coated with frost behind the rear wall of freezer. I cleared the air duct that leads down to the lower refer portion (sight ice blockage) and I though I fixed it. Today, I investigated the thermostat. I turned the thermostat all the way up (just before off) and the motor kicked off and returned the dial slowly and the motor kicked back on so according to the diagnostics that means its working (sort of). So I then checked the freezer control and it seemed to be stuck on MAX so I manipulated the arm to a vent and it broke free of ice or something. So I imagine the operation is like this: The refer control turns the entire unit off and on with varying voltage (per the spec of the stat rheostat) to the compressor and the freezer control seems to manipulate a 'bleed door" to feed the lower refer portion. Min freezer setting is bleed door wide open to refer section so all the cooling is sinking to the lower portion. MAX setting is bleed door shut or restricted to keep freezer closed to refer section. Does this sound correct? I need to wait 24hrs to see if my recommended setting (3+3) refer/freezer setting is going to get my refer portion back down to >40. Fridge is ~10 years old, new from Home Depot. I had a line on a 25' stainless Samsung that only needed a door latch for $300 but I missed it due to no truck at that hour.