Hey-yo another STL folk here!! Glad to have you on board.
If you're worried about becoming too small, try adding a strength/lifting regiment. That will put some healthy muscle back on you around those ribs (and arms and legs etc.) I do the "Five Essential Primal Movements" as outlined in the free eBook available on this site called Primal Blueprint Fitness. I try to do that every 3-4 days or so.
That's all I got. From a diet standpoint, I'd say you're pretty much dialed in. Don't change anything if what you're doing is working. Just keep enjoying good Primal food and follow you're body's signals as far as how much to eat.