i'm pretty sure i cured him because the werewolf event is all done,and i have been doing his newer lycanthropy repeatable,maybe it's because i didn't run to help him first instead of bernard,or maybe it's because i let him change and then i had to go and snatch him from the forest
First you should choose Logan over Bernard when the werewolf attack. Then try to stay with werewolf Logan all night. Give him three wolf banes and then give the true cure. This should be enough.