IMO, "whatever" means I have no time for this or it's a moot point; "I could care less" means I do care but am trying to save face or convince myself and others that I'm not emotionally affected by something /someone.
The phrase "I could care less" is intended to mean 'I couldn't care less', or 'I don't care at all'. The ex<x>pression 'I could care less', frequently misused, actually indicates that one does indeed care, at least to some extent.
I've never understood that,in my neck of the woods the saying is"I couldn't care less",which at least makes sense.."I could care less"surely means that they care somewhat...
It means.....go **** yourself...when I say it.