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I doubt there is a single answer to your question. I don't think hand pressure could deform a person's skull without some extreme effort and leverage. Some skulls had thicker/stronger bones than others. Soccer players have been observed to have thicker skulls due to the repeated trauma of heading the ball. Bone strengthens when it is repeatedly put under stress.

Before the sutures between the plates fixate, some movement of the skull plates would be more possible. Sutures fixate in most people during the middle to late teen years with the extreme happening in the early 20's.

Cranial Sacral Therapists claim otherwise but research indicates they are wrong.

The forces measured in the helmet industry usually pertain to G forces related to concussions as in football helmets and other high speed forces related to fractures as in motor cycle helmets.

What is your objective with this question ?