K-PAX ending explanation

In K-PAX, there are two possible explanations:

1. Prot is crazy.


2. He is truly an alien.

There are facts that indicate 1, but also 2.
Examples:

He seems to respond to hypnosis, has a sort of phobia of water, looks just like his friend and doesn't physically leave. But he sees UV rays, finds his planet and in the end makes the other patient (Bess) vanish.

How should the whole movie be interpreted, especially the ending?

Answer

Prot is human

• Prot has a human subconscious


• Prot has a human history (e.g. the school book, and the probable trauma)


• Prot remains on earth after July 27th

Prot is an alien inhabiting a disturbed human's body

• He can see ultraviolet rays (perhaps through the glasses)


• He has an astounding knowledge of astronomy, physics, and advanced psychology (cures patients of serious mental illnesses that are equal to his own if he were human)


• The electrical disturbance on the surveillance when he 'left'


• He managed to disappear and survive unnoticed for almost 5 years since the incident.


• He evaded security and left for 3 days completely unnoticed.


• He left Bess's letter on her bed before she disappeared, confirming some sort of interaction that allowed her to disappear unnoticed on July 27th. (Perhaps he told her of a way to breach security)

Prot was an ET and could travel through a light beam in human body physical form but only one at a time. Hence, "I can only take one of you" ultimately choosing Bess.
Robert Porter was Prot's human friend before suffering mental trauma and becoming catatonic so Prot occupied his body to protect him and travel through until he could deliver him from peril after finding the right caretaker (Dr. Powell), then catching his prearranged travel timed Lightbeam Home using Bess as his human form (Vehicle), leaving Robert in safe haven with Dr. Powell. That's my synopsis.

Regardless, Prot acknowledges his return to consciousness with Jeff Bridges, asking that he take care of him. To me this says that although Prot may be an alien in Robert's body, he may still maintain some of the human subconsciousness.
For these reasons I find the clues are more consistent with the possibility that he is an Alien, than he is not. Funny enough to say, it would be almost more convoluted to argue that he was human.