From what I hear, most on-site fillers use gas to gas instead of liquid to gas, so you end up with less in the tank after all is said and done.
In my area, cost to swap a 5 lb cylinder is $20. Cost to swap a 20 lb cylinder is $30.
This. I just had this experience with a shiny new 20 lb aluminum tank with handle. Very sad.
As for freezer at refrigerator temperatures - I'm building a side by side into a kegerator/lager fridge too -
Mine has dials that set the temp for freezer and refrigerator side and they're in the...