sounds like he needs to take a decent long break – a minimum 4 weeks preferably longer – a couple of months could be a good plan [give his body a chance to recover from the long term disturbances of its chemical balances which is likely to be what has caused the nightmares]
the nightmares should become less intense and occur less often as his body recovers – until they go away/stop he should stay off the pills
he also needs to be aware that they may come back if he starts taking the pills again – in that case the only thing he can do is decide if the pros of taking it exceeds the bad effects – a decision only he can make
