Hmm imo a good sit down talk might help. Have pen and paper or even a posterboard handy at the table... talk (semi-adultly) with him, discuss the various "rules" you have, and then agree upon the consequences.

Hopefully he will contribute and talk openly with you. This way, when he does something "wrong" it isn't YOU who is doing the enforcement, but the 'agreement.' This way he knows the rules, and he knows the punishment... and it helps you hold to good discipline also.

BTW try to give reward/praise for the good things he does in his daily routine, that will help him receive your support and attention and encourage him to do more "right."