Hello! I think your best option is to handfeed him. You know he’s full when his crop starts to tighten. However, if he doesn’t want to eat don’t panic. I have a cockatiel that eats when it wants to, and not always when she should. However, if you find it’s not eating at all, maybe check with the vet again. I’ve heard about this happening from time to time with cockatiels. Parents tend to care only for the strongest chicks in some cases because it can get very tiring for them. I’ve also read about fixing splayed legs in young age. It is fixable if the chick is young enough. So what I’ve heard is that you should use wool or sell-o-tape and wrap it once around the chick’s legs under his knees, I think. Don’t do it to hard, but just as much so that the chick has a normal posture and soon enough he might grow into it, then later it can come off permanently. I think you should change it quite often. When I first heard about this I thought sell-o-tape was quite strange, but that‘s what I’ve read. I suggest you look up about it though. Hope this helps! Hope the chick is alright!!!