I don’t want to worry you unneccessarily, but I’m concerned about his legs. Are they always splayed out like that, or does he ever get them under him like a perching position?
We raised a splay-legged baby budgie. One of the things we did for her was to take a sock and stuff the toe into the open end to make a little “sock donut”. Then set your bird in the donut with him legs under him so he’s partially supported in a sitting-up position.
We ultimately had to actually use veterinary tape (NOT adhesive tape!) to tape Scritch’s legs together so she could grow straighter. It had imperfect results; she has one leg cocked out to the side and has some trouble stepping over things. But she can perch.
I want to emphasize that I can’t be sure from the pics there is even a problem. However, in general, you want him too be gathering his legs underneath and starting to support himself. Try a sock donut for starters. We put a liner in it of one piece of tissue that we could change out every time he pooped --save a lot of socks.
Another nice trick is to put grains of dry rice in a cloth bag and microwave it for a short time. Take it out and it should radiate warmth for a while. Wrap it in a towel or something to prevent direct contact with hot parts, and set it next to him, if he needs more warmth.
Best of luck to you!!! :>