Parody Lyrics Copyright Question? Please help?

There are some instances where you are allowed to use copyrighted material without permission. This is called "Fair Use". The "Fair Use" rules make a distinction between "parody" and "satire". If your "spin-off" lyrics poke fun at the original song, that's parody and is allowed under Fair Use. If you're using new lyrics to criticize something else, it's satire. Satire is sometimes allowed, but other factors are considered, including whether you're making money from it, and it's effect on the original work.

Since you're not making money and it's unlikely your lyrics will ever have any harmful effect on the original lyrics, you're probably fine.

No, copyrights are for original works and can be messed with, as long as over 50% of the work has been changed