You seem to have neurological symptoms rather than just eye strain. Please read this link to see if it describes you in any way:
http://www.neurosymptoms.org/#/visual-symptoms/4539525685
If it does, you might want to navigate through the site for whatever else interests you...
Unbearable burning in the eyes when looking at a monitor has always been a PWM problem in my previous experiences. It is still highly possible that the Viewsonic had PWM after all. We cannot rely on reviews for PWM because the manufacturer may change the PWM of the monitor at any time. The only...