Where to start...
The numbers next to each body part does refer only to hit%, you will notice them change in slo-mo as the enemy moves about behind cover or if an arm twists out of view, etc...
The solid bars UNDERNEATH those numbers are the general state of the limbs(not health). If you keep attacking an arm enough for instance, in VATS you may notice that arm's bar will be empty compared to the other limbs. That limb is disabled and therefore the enemy may have trouble aiming now, or it may be dizzied or blind if it's the head, or if a leg goes out, then it will be slowed and have trouble rushing you, etc...
The perk that shows more info refers to the red info bar at the top of the screen in VATS. It shows the monsters overall level, and various icons stating its defense attributes. You will see a shield icon which refers to general ballistic power, or a lighning icon which is for energy based damage, etc... The higher those numbers, the less damage that type of ammo/attack will do to the enemy.