Good for you for being a Dad and taking time with him instead of uploading pics. Much respect man.
So, the black screw that is a Phillips head right by your throttle cable is backed all the way out? I can't tell from the pictures.
Can you manually without the engine running close that butterfly to touch the black screw?
Have you switched the spring and solid linkage? The spring is a little bent but, not sure that matters.
If none of that does it, someone else may be able to help you.