Based around Jon's current travels and "extra curricular activities"
in the locations he is currently visiting im inclined to think that he is more likely to suffer from 'Neurosyphilis' than 'DID'.
(Commonly called Brain Syphilis, Neurosyphilis dementia is also a psychiatric diagnosis wherein a multitude of atypical anti-psychotic medications are used to help control the patient's irrational behaviors, with limited success. The term is used in traditional classifications of organic disorders of the brain).
1. it would explain the sudden behaviour changes.
2. His lifestyle increases the likelyhood of Syphilis being contracted.
3. The part of the world he is currently in has a larger infected population than western Europe.
4. It amuses me to take the piss out of him