I can't help on the theft, but if you are using that much beer and you have foam issues, try the BeerBlast Mixed Gas Generator. It can reduce/eliminate all your foam issues. We have bars saving 10% waste immediately. Reduce CO2 costs and pour a better tasting beer (less CO2 used in pushing, CO2 is bitter tasting).
www.southteksystems.com There are many distributors and your gas company may already have this option available to you.
Also, check the temp at your taps. you should be 34-38 deg in the cooler and at the tap. Any warmer and you will see foam. good luck