First of all I’m not a baker, but you do know you’re putting a lot of effort into this right? I mean I would be content with store bought cookies, you made him a freaking wardrobe already ;) As far as I know, if you make the dough yourself it will fill out when heated. Are you sticking to that recipe? because in the picture you can clearly see that they put wads of dough in there that shapes itself when baked.