I used to keep my bunny, Pongo, in his cage for the majority of the day, letting him out to play in my bunny proofed bedroom for about 4 hours a day. Progressively, he started hating being in his cage and would CONSTANTLY be chewing on the bars and scratching at them (he eventually learned how to push the cage door open, somehow) and I could never get any sleep. I ended up leaving him out his cage constantly, as you would let a cat (in a bunny proofed room, of course, and it helps that he’s potty trained). I don’t know if this would be a viable option for you, but I would consider it if letting him out of his longer than what you’ve been letting him doesn’t help. Really, he’s chewing his cage out of boredom. Especially a 5 month old bunny who’s reached/reaching sexual maturity, he’s got all of this pent up energy that he needs to release.
I truly believe that any disciplinary action won’t work, since you’ve already tried to discipline him. You shouldn’t try disciplining a rabbit who just wants to release his energy that he has stored. He needs to be let out more and exercised.
EDIT** I also recommend getting him neutered, as that will also tame him.