I tried something vaguely similar with completely different assumptions. I basically ignored the number of animal deaths in favor of minimizing the amount of animal torture. The whole thing was based on how many animals it takes before empathy kicks in, rather than an actual utility comparison.

I instinctively distrust animal-to-human utility conversions, but the ideal version of your method is better than the ideal version of mine. I do recommend that meat eaters do what I did to establish an upper bound, though. It might even convince someone to change their behavior, since it's based solely on convincing the human they already have the preference for eating less meat.