T.H.
I would let him feed himself as much as he wants. Self feeding rocked my world! My daughter refused anything on a spoon at 8 months so she fed heself everything, and she seriously ate like a champ then too! I would say any meats you're eating, he can eat too. Crackers (we like the baby Goldfish), bagels, and bread are good, pretzels, cheese sticks and slices...you name it, if he'll eat it I'd give it to him! Stay away from raw veggies for a while yet though.
He gets all the nutrition he needs from the formula so everything else is just extra nutrients and extra practice and feeding himself. I wouldn't really limit how much he eats, just give him healthy things.