you can't get in trouble for just knowing a password. as long as you haven't broken any rules, you're golden.
if they know the kid got the right password from you, giving them the wrong one will only make you come off looking like a lying weasel, meaning they'll be harder on you when punishment (if any) comes around. just be honest. confess your fears and motivation for screwing up the password on purpose and be completely open with everything. otherwise, you're going to make life a lot harder on yourself.
This happened too me alot in 8TH GRADE! It was pretty funny though. It always seems that I knew peoples passwords, And people knew that I knew them. And low and behold, I send 1 'explicit' email of someone's account, and BAM! Everything is on like a lock down! Word of advice: Play dumb [If it's not too late] Ask totally retarted questions such as: What's a domain? So the domain is the same as the passord? etc... (If they don't see right through this, You should be fine) WARNING: I am me, If this worked for me; It is because of my dumb luck, Don't try this at home. If you chose to ignore this warning, You do so at your own accord.
covering your ass after the fact normally makes things worse. you need to plan things out ahead of time if you want to get away with them.
Covering your ass is the best way! Even though, YOur writing did not make sense to me, (as i could not decipher it, MY FAULT) I think you should continue your covering ass teqnique. +You should stick to your story,
once you've already screwed yourself over and changed things several times, it's hard to stick to a story. i'd just come clean--if you're honest, the consequences, if any, *should* be less severe.