I cannot fault your logic except in regards to the granny/girl scenario.

I know plenty of grannies that have more potential for enjoyment than suffering than many young girls.

She could be a saint upon whom many thousands of people depend for their own happiness. And just real talk this girl could be a total bitch, self centered and greedy with exactly zero chance to effect positivity in the world.

Human value absolutely boils down to the three categories you listed, but ultimately it's who determines the criteria that determines each ones value, no?