The laws of physics in Highlander's universe

The 80's was a decade that gave us some of the most momentous moments in pop culture history. The bulk of which is comprised of action  movie classics like; Robo Cop, Return of the Jedi, Predator, and Aliens. Many were flavored by the time and consisted of sometimes ludicrous action scenes with laser guns, massive explosions, sword fights, and enough ammo to outfit small armies. Then there was Highlander, an action film that satisfied with its down to earth sword fights and totally awesome Queen soundtrack. However, music aside, Highlander is a dramatic story about an evolved subspecies of humans that are born immortal tied to the very life force of the earth, no it's not Avatar, and to understand more of what their power holds they fight each other. It is never stated why they must kill each other, perhaps a test from on high to see if mankind is worthy of their gift, but that is beyond the point. They fight and absorb the souls of the defeated and with each victory they gain power. That is where a conflict occurs in the movie. Like their destiny, it is never stated that these chosen are superhuman, just that simply they can not die unless the head is severed. So, why is it then that some of the feats they perform are so insanely powerful, and inconsistent? 
The first major test or display of this power, and physics, comes a little after the first third of the movie. The main villain Kurgan tracks down McLeod's abandon stone tower home hoping to kill our hero so Kurgan may adsorb his soul. However, he finds a man named Ramirez's and McLeod’s wife as Mcleod is away. A fight instantly ensues upon Kurgan entering. Like many other things it is never stated how old Kurgan is but it would be likely that he is at least two hundred years old at this point in the movie. Ramirez on the other hand states that he had lived for over a thousand years as an immortal, and that he has traveled the world. He taught Mcleod to fight so it would stand to reason that he is far stronger than Kurgan. Kurgan even calls him by name, so  it is implied that Ramirez and Kurgan have fought before. Mid way through witty dialogue a frustrated Kurgan is is out matched by Ramirez, and with the help of rather explosive lightning, is pushed off the steps of the tower. Kurgan then falls at least two stories to the floor and is then buried by large stones from the wall. Kurgan immediately emerges from this seemingly no worse for ware and continuous the fight with a new rage. He overpowers Ramirez and with a single blow destroys a large section of the tower wall. Kurgan then knocks Ramirez off  balance and smashes him in the chest before killing him.
Many castles of the day in Scotland where built of sedimentary rocks; limestone, sandstone, conglomerate, etc. These rocks, while solid, are easy to carve and place so they made for good building materials. Kurgan sword, and Ramirez’s sword, which McLeod later uses, are specially crafted but still are made of forged iron. The force needed to break apart several hundred pound blocks would have shattered or at least cracked Kurgan's sword, and even if it had not, the blow he delivered to Ramirez’s chest would have transferred to the stone steps he was laying on  if his strength was consistent.. Not to mention completely collapsing Ramirez’s rib cage.  

To the fall that Kurgan took, when talking about force and reaction, you would think that the sudden stop as flesh met stone floor would have killed him, if not rendered him incapable of action for a long period of time. The movie never seems to clarify the line between reality and what magical force is in place. It is understandable that these immortals are more than average, they can harness a power and live long enough to gain near superhuman skills. Still a human body falling from 20 feet would be more than enough to break most bones in your body. It is not far enough to reach terminal velocity, but still the end result is not in anyone’s favor. Lets not forget the several hundred pounds of rock that landed on Kurgan after he hit the ground.
Another issues of force is the energy imitated upon felling a foe. With each kill the souls is absorbed causing intense light and energy strong enough to lift or move the victor. Often times it causes shortages in cars and electronics nearby. Light objects are moved as if by a gust of wind and heavier objects are jostled, but given that this force can easily lift a man there should be more impact upon the environment. Glass would / could shatter, and cars would / could be shoved to one side. We see examples of this throughout the movie, often times the effect is tied to the importance of the kill. The final fight, called the Quickening, is the greatest display of this power. Though by the light show and wind it produced you would think that the entire building it occurred in would be reduced to rubble, or at least knocked off its foundation, instead of just breaking the glass of the windows.
Other examples of rule breaking physics fall into place along the lines of well established Hollywood tropes. Guide wires and one way reactions to bullets have been used to the umpth degree to achieve desired levels of action. In the first fight of the movie, between Mcleod and a french immortal named Fasil, we see Fasil nimbly jump from car to car with ease, with hardly any physical contact before launch. and flip backwards at least 10 times before jumping again onto a car to pursue Mcleod. While the ladder is not extremely physics breaking it is surely beyond normal human capacity to not vomit from vertigo.
Before the last fight of the movie we see Kurgan fighting a long time immortal friend of Mcleod and after Kurgan's victory is witnessed by a gun totting Reagan patriot, he is literally blown away by an entire Uzi clip load of bullets. Kurgan's chest is riddled as he falls back, but the shoot is barely affected be the force of the unloading clip. However, a 18th century duel is shown where Mcleod is shot several times by a flintlock pistol. Upon impact he simply reacts and falls to the ground. While the shape and impact power bullets has changed significantly in the past two hundred years, the difference in action / reaction would not have been that stark.
Lastly, another example of action and reaction not quite adding up, there are at least three moments in the movie where sword strikes have landed in such a way that it would normally knock the wielder off balance. The best scene is in the last fight where Mcleod saves his new love interest from a viscous downward strike by Kurgan. By his double gripped over the head pose it seemed that flush with ecstasy and rage Kurgan was intending to cut her in half, and if Kurgan could blow apart stone with single gripped strike the blow would have indeed been devastating. It was not be though, because our hero managed to block the strike by extending his blade to intercept Kurgan's strike. However, again if Kurgan could smash stone how strong would Mcleod have to be to stop his strike cold. If the rules of reality had been followed more closely McLeod sword, which is Ramirez's iron folded katana would most like have been shattered along with Kurgan's blade. Given that the McLeod’s sword cracked after a blow to a concrete pylon it would stand to reason that both blades would break. That or the blow would have been stopped but not before both swords smacked her in the head. 

Highlander is a great popcorn flick full of 80's tropes and action. It followed along the vein of mystical movies that where popular at the time, but much like those other movies it failed to dictate the fine rules of what “magic” was in the movie. Other movies, like the Harry Potter films, handled magic very well. It was a core piece of the universe so it could not be flung about without issue. With any movie really, magic or mystical forces must be dealt with in the same way any other force / energy is dealt with. There must be rules that keep it in balance. In Highlander's case there seem to real lapses in just what the limits of the power  are they hold. If not magic than just plain simple physics must be put in check. When you watch the movie you’ll see it best in Mcleod only lodging his sword into concrete with a two handed grip, where Kurgan manged to blow apart a castle wall with only a single griped thrust.