The problem with leaving him alone wiggling around, is that his legs will not ever come together. Splay leg in older chicks cannot be fixed. His legs look wider than most, so he might not improve if he has hip problems. But vitamins, trying to work with him, and whatever you can do may help eventually. Handling him under the heat and trying the hobbles is what I would do. My only chick with this really had a tough time at first, but eventually could walk normally.