I haven't gotten too far but this should give you the highest MAX level and past Boss 6 but before boss 5. (I beat boss 6 before boss 5) Here's the password to where I am now. The passwords are written just like how you would type them in so the upper password and the bottom one..
V81GDG0R00 There are no letter O's in this password only number 0's.
Here's another password
4G213DBO10 Right after the B is the Letter O