My rich custodial father is unwilling to pay anything for college. So, can I not include him in CSS?

OP’s question was can he leave father’s info off the CSS. No, he cannot.

Even with parental support it is difficult for international students to attend college in the US if they have high financial need. Their employment options are limited. Their travel costs are expensive. Their loan options are very limited. Most schools are need-aware for admissions for internationals.

It’s just very difficult.