They kind of gave the ending away right off the bat with the numbering but I enjoyed the process.
And yes on the 'me' ending making things ruder. You see it used a lot in gangster and Yakuza manga. He's basically saying 'You f$#&ing monster' or 'You goddamn monster'. Of course not all words ending I me are rude, like 'dame' isn't rude, it's just when you tack it on to another word, like 'aitsume' is 'that f&+$er'.