I followed the game and even I could tell easily by the end that adonai was a monster even without the last breaths. He's too smart, a monster would've killed him...unless he is a monster.
And to pick adonai's word over Sirusboon's and Urameshi's...
adonai - uncomfirmed role/race
Sirusboon- Confirmed- unconvertable
Urameshi - He went to kill the head wolf. He is trustworthy for that.
Whilst I agree adonai didn't break the rules as such by using a fake pm as proof, if only you'd re-read the rules on seeing that posting pm's confirming roles from Chaoswind was forbidden, then you could call bullshit on him.