Are you a psychiatric nurse? I believe a licensed psychiatrist would be only the person to make a proper mental diagnosis, so by you stating that LL is incorrect is just as erroneous. She is in an environment, like yours, that puts her in close contact with mental illnesses.
From my knowledge, there are different "levels" of schizophrenia as with many disorders like bipolar. Delusions and hallucinations can vary also. Steven may have been a religious man with beliefs of speaking to, hearing from, getting spiritual revelations, and maybe even blaming God, true, but most people do not let this get to a point of dysfunction with everyday living. Something has. You have selected a few of the symptoms or characteristics that LL has posted from her research. She is asking to look at the broad spectrum presented and is not diagnosing him and stated so in her post. It's something she is theorizing... and backing it up with facts as presented....and I think she has done a very a thorough, and thought provoking job of it.
As gsmith brought forward, SK was taking some kind of medication. Was this a prescribed medication by a doctor? Was it something he got from a friend, acquaintance or off the street? Or was it something homeopathic or an illegal drug? His family has not come forward to say he was on any type of medication. ???
Lady Leo's theory and speculation doesn't ask for approval, but it's been presented for thought and discussion. It's plausible that Steven did suffer from the onset of schizophrenia or another undiagnosed mental illness. This is why I ask if the marks I had observed on his head in the one video were scars. ??? Severe head trauma, I'm sure you are aware, can cause negative cognitive results. There have even been studies on people who have had head injuries and have shown schizophrenia like symptoms. Most with that study ---lacking the characteristics you have chosen in chronic delusions and hallucinations. I know from personal experience two people I had close contact with that had head trauma. One in his early 40's who had been unconscious for 2 days, and the other (early teens) in a coma for over 30. They both had to have rehabilitation, but obviously in the latter case it was extensive. Depending on where in the brain the injury occurred, it could be that life long medication is essential in dealing with the mental ramifications; especially disorganized thought patterns. From my personal observance, they show slowness...in speech and thought...even if barely noticeable upon talking to them, but as time went on you knew something that was once there...wasn't working the same and probably never back to the fully functional person they once had been. The latter had problems with decision making, etc.(disorganized thought). Ironically, like Steven, they were both gentle souls...but I did observe that they had a hard time dealing or expressing their feelings when upset afterwards. In the young man, I gave him a guitar I had when I was young...and it was an inspiration to him...in which I was so gratified to see him embrace something with such positivity. Odd too, the 40 year old was a musician also. Therapy comes in many forms...and music therapy has been known for thousands of years...just not recognized.
With that, I'll close on a good note.
ETA: For those interested:
http://www.schizophrenia.com/diag.php
http://www.neuroskills.com/tbi/bfrontal.shtml
but what I was stating, was exactly that- only a psychiatrist can make a proper diagnosis* and while we can say we think someone had something we can't say he had a disorder with an extremely *high* degree of confidence. I consider schizophrenia to be an extremely specific diagnosis and 90 percent to be pretty high, so I challenged it. And you are free to disagree (even vastly!) from the challenges I made, just as I disagreed with hers. Your post is exactly one reason why I say we can't say with a high degree of confidence he had one specific disorder. 
