The springs in clutches are designed so that when fully depressed, pedal effort is reduced. When springs weaken the peak effort may be reduced, but the fully depressed effort usually goes up.
The clutch uses brake fluid from the brake resivoir. If there were air in the line (or brake fluid leaking under dash at firewall) the clutch would become soft and hard to dis-enguage.
If the clutch were slipping, the RPM's would go up but the car would not move.
I'm not sure what to make of your symptoms.
Perhaps you are suffering from hesitation?
