Just for another option, if you like the Savage Worlds system, Realms of Cthulhu is pretty fun. It gives you options on how to run it and keep it gritty or pulpy as you desire, and the small adventure I have played in it was a blast.
Not sure about it for the Dresden rules, but if I was going to have to, I would do something like the hunger stress track rules for sanity, as represented, though you will have to decide how you take sanity stress to begin with. The Discipline roll to overcome it at the end probably makes sense. One recommendation, lifted from the aforementioned Realms of Cthulhu: When the sanity stress track causes them to take a consequence/insanity, keep it separate from the rest instead of having it take up an available consequence, and then reset the stress track. They now have an insanity. When they take another consequence, they have another insanity, or ramp up the first one.
If they are ever taken out from too much stress/lack of available consequences, then they are stark, raving mad/full on cultist, and no longer playable, at least not without a LOT of time in an asylum.
The real question is, how lethal do you want the system to be? Cause the usual answer in Cthulhu games ranges from, "very," all the way too, "how on earth did you even get to the table??"