Stewie has agreed to lower your ban, as he believes he has overreacted.
I have looked over a few things, and I can see that the ethos has not wholly been followed here, Stewie has stated that this was because of his overreaction, and so the ban will be lowered to time served so far. You were however causing problems ingame which led to this situation, and even if the ban was incredibly harsh, the ethos also states that punishments given are at the discretion of the staff member.
As long as you were actually breaking rules, which you were, this punishment is still valid, which means it is not in itself abuse. No action will be taken against Stewie, since his intent was just to do his job and punish you as required, regardless of whether it was harsh or not, however I will speak to him about ensuring to keep punishments and bans a bit more lenient than this, and remind him that the ethos requires him to use other methods to reach a conclusion to a situation, as opposed to going for the ban command immediately.