Im just going to congratulate you for being a great role model for this young boy! Tough love is always tough but as the others have said 'like toddlers if we as parents dont follow through with consequences kids will get away with murder (so to speak)'
I know all too well of 9 yr old behaviour and how rude and arrogant they can be as i have a 9 yr old boy myself. Another thing to remember dont forget about 'growth spurts' and spurts in testosterone as this can alter behaviour sometimes as well. BUt after saying that your child still needs rules and boundaries having growth spurts or not.

I think the removing the bedroom doors and toilet paper is a brilliant ides .... Dr Phil type rule but if it works well use it.

And lastly i have stepsons as well but they are older 14 and 18 and god do i know all about moods ..... and all about their dad feeling guilty too if he puts too harsch rules down they will just leave home .... so darling i hear you and i take my hat off... !