They're competitive. Just pick one
Sole or shared custody is not related to child support.
Child support is for the support of the child no matter who the child lives with or how often the non-custodial parent visits the child.
It's determined by the court usually, based on certain formulas available unless all parties aghree to a certain amount.
I don't think so. Who's fault is it that the parent didn't visit? Not the child's.