We've been using antifreeze& water in rear tires for probably 40+ years - maybe longer. My earliest memories included Dad telling me about the antifreeze in the rear tires on a WD45 or a D17.
We haven't been trying to put 1/2 antifreeze and 1/2 water in the tires - we really don't need protection down to 40 degrees below zero! And, if it does freeze once in a while no big deal (I've driven an AC 200 with frozen ballast for a while. It thawed out later that morning, and at 5 to 6 mph it was no big deal. That was with 23.1-30 rears. I wouldn't do heavy tillage with frozen ballast, though.)
We usually put about 1 gallon of antifreeze in the front tires and maybe 2+ gallons in the rears depending on how large they are. Protection down to +10 degrees would be more than enough down here (I'm in SC, about 50 miles above Columbia), but I doubt the 2 gallons protects much at all. Really we're using the antifreeze fro corrosion protection as much as anything. If I remember correctly we put 2 gallons of antifreeze in each rear tire on a tractor with 16.9-34 tires on it and we use it to feed hay all winter. No problems.
I'll see about getting a chart together that shows some tire sizes and the gallons of water needed to fill them to the top of the rim for ballast and put it on my website (link below) later today. That way you can make your own decision about how much to put in based on your temperatures.