stuck sheds happen all the time, I see you have already tried to raise your humidity, if you dont do that successfully you will have bad shed problems over and over again. If a snake is not shedding properly, usually the humidity isnt where it should be. The shed should just come off on its own, next time, when you notice him shedding just start "misting" with a spray bottle and water, that should raise the humidity and help in shedding.