To start, I will agree that; everything we perceive is contained within our brains, and I agree that to believe Man is unable to understand something without the proper research and rationalization is intellectually dishonest. With that in mind, I hope you will agree that the study of Law is a subset of Philosophy, that Science and Philosophy are two distinct study disciplines, and that science is unable to answer questions regarding value, morality, and the metaphysical. I also hope that you do not deny that there is an immutable relationship between Science and Philosophy and philosophical discussion heavily influences scientific theory.
They are both bound by logic, so i'm not sure if your argument does anything in terms of religion.
So, what about Natural Law? Natural Law is not man made and Man does not govern Natural Law. Cicero, Plato, Aquinas, Hobbes, and others agree that natural law pre-existed man. The writings of Augustine of Hippo, Sir John Fortescue, Sir Edward Coke all show that natural law and divine law are ontologically connected within Man's existence and that all other laws are derived from natural and/or divine law. Sir Edward Coke and others concluded that it was human nature that interpreted the purpose and applies meaning to natural law. And, if Man interprets and gives meaning to natural and divine law, it only confirms that natural and divine law pre-existed Man. So, in that sense, you are correct that religious laws are enforced by man but that in no way means natural and divine law was created by man. If anything, the study of Natural Law concludes that all laws created by man are derived and based on an order given at the time Man's existence began, that the basis for all laws (religious, civil, and legal) pre-existed Man.
I'm not sure why you combined the ideas of natural and divine law in the middle of your argument. You don't provide any reason why either. Natural law is just a theory that arose through philosophical debate to explain why men create laws. If you divine natural law from the idea that we didn't kill each other off in our early years i would argue that it was clearly genetics that govern this. Some animals kill their fellow species, others do not. Its based on their genetic makeup. We all have the "same" genetic makeup so it makes sense that an underlying level of similar expectations would arise. If you look at other species this becomes abundantly clear.
I would also argue that natural law as we perceive it would not exist without us, thus it is a creation of ours to understand our perception of our own tendencies. Would a species with a collective mind behave under a different set of rules? I would think so, plus natural law can almost be viewed as guidelines (edit: instead of guidelines think of it as an explanation of the normal tendencies of man, obviously some vary from this) as it is broken many times over and its not in any way absolute.
Science can not explain the spiritual side of a human being. All science can do is manipulate the chemical nature of Man to show (for example) that an increase in alpha waves results in a feeling of relaxed alertness; science can only measure the end result. That manipulation can and does not explain the origin of the emotion or explain why individuals feel differently as science is unable to explain the value placed on the feeling, the morality that leads one to feel one way or another, or the metaphysical nature of the emotions.
Again you broach emotion as being unexplainable when it most certainly is. The interaction of millions of brains cells is a complex matter that is beyond the scope of just about everyone who is alive today. Then you add in chemical reactions through glandular processes and its becomes even more complex. You say science can not place a value on feeling yet removing part of the brain can drastically change EVERYTHING about a person including their emotions. There is a reason behind this.
As far as the spiritual nature of Man, all one needs to do is read any psychology or philosophy to realize that the mind, body, and spirit are intertwined into Man's existence. As noted above, there is an immutable relationship between Science and Philosophy and science requires faith. Even the most rational and reasoned of scientists are unable to deny that they require some level of faith, no matter how diminished, in order to form a hypothesis.
So, spirituality is not an illusion created by Man, the scientific/atheist mind is spiritually sated through the creation of hypothesis, denying the spiritual side of Man's being contradicts thousands of years of philosophical reasoning and scientific method, and ignoring your inherent spiritual nature can lead to living an unfulfilled existence.
You never explain why science requires faith, it doesn't. Coming up with a theory doesn't require faith because it is either right or wrong. If you don't approach it from this perspective then you are not being a proper scientist. It absolutely blows my mind that you think it takes faith to form a hypothesis. I'm sorry but you couldn't be more wrong, all it takes is perspective and creativity. Do you think einstein required faith when he figured out gravity bends spacetime? No, he viewed a guy falling off a roof and realized that gravity doesn't pull, only that space pushes. To come up with this theory in no way required faith.
The Scientific method does not have anything to do with spirituality. Combining the two is just wrong, science split from philosophy for a reason, yet you seek to combine them again. Like i said, forming a hypothesis doesn't require faith and doesn't result in a renewed sense of spirituality.