Prot was a spirit who was Robert porters guardian Angel over the course of his life . Robert porter over his years would pray and ask for guidance and help when in need and prot would come to take care of him and offer him guidance
Proat loved fruit and was especially interested in the red delicious apple in the psycologist office because where he is from someone ate an apple in the garden of eden and got in big trouble (eve)
Prots report was some of the mistakes he made in his life on earth that he had to fix
He traveled by light , the same thing it is said that we see and walk towards when our spirits pass on after our death.
The one patient was cured of his problem of not going outside wearing a mask for protection etc when prot instructed the other patient with the glasses to strangle him so he would die and be brought back , showing him that there is something great that happens after death and not to waste his time being afraid of dying
The mental patients saw prot as the Angel he was, not robert , because there minds were more open to seeing things that you cant really explain .. this explains there comments of "whos that guy " thats definitely not prot when Roberts body was taken out of thre room after prot left him .
The last comments on the movie about the world expanding and contracting refer to birth and death
Having to repeat youre journey over and over untill you get all your mistakes right is reffering to the journey we all are on untill we serve gods purpose here , and get invited back to our home heaven.
If we get it right the first time ...we dont have to keep coming back like he did untill we get it right.
K PAX was inference to heaven not a planet