Joy of Pickling does meet all USDA standards for safety. Linda Ziedrich is a documented food scientist. You'll find a few recipes in the Ball books and at NCHFP that allow for slightly less than the 50% minimum of vinegar but they have been tested and retested and hold true due to other factors in the recipe. I wouldn't be concerned about this one. The 50% minimum rule is primarily applied to untested recipes or unknown source recipes.

One trick you might consider to resolve the ice problem is just to squeeze into the freezer a couple of doubled-up sandwich sized ziplock bags of water to freeze (those small lunchbox plastic freeze things work too). You can then just add them to the brine to help keep the brine temp reduced.

Dave

Thanks, that makes me feel confident in the recipe.

I might be able to squeeze a bag of water into the freezer that way. Good thinking.