You may be able to reset the user password and erase your personal
files.. This, after making a second Admin user account. ~ Then Mac
hopefully could be started into new account. (erase old, after?)
• Reset an OS X 10.6 Snow Leopard User's Password - Without a CD/DVD | T. Williamson
https://www.tannerwilliamson.com/password-recovery-reset-an-osx-10-6-snow-leopard-users-password-without-disc-disk-1468/
There was more than one article on how to reset the Mac OS X
etc; change user name, make new admin account to facilitate
this idea. ~ One I found might not be the steps required though.
Without the DVD/CD media.
Perhaps this idea may work.
Maybe other article told of different code for 'terminal command-line'.
• Reset Mac OSX User Password Without CD with command line
https://brakertech.com/reset-mac-os-x-admin-user-password-without-cd-disk/