This is a fairly old post but I had a similar issue and found a solution so figured I should share it.
Increasing the gravity scale will only just effect the acceleration of the fall and your jump.
Changing the weight will have a very similar effect.
If you want to increase the max velocity of falling, that can be found in the Project Settings under Constraints titled “Default Terminal Velocity”.
By default it is set to 4000, which is actually a fairly realistic number. Additionally, changing this will also change every physics asset that isn’t specified to have a lower terminal velocity.
I hope this helps.