Booting into runlevel 1 shouldn't be a problem. Your problem might be that the password is not stored in /etc/passwd but in /etc/shadow. Note: back up /etc/shadow before editing it!
The entry in /etc/shadow on my desktop looks something like this:
(I replaced the actual encrypted password with "this_field_contains_the_encrypted_password" for illustrative purposes). I believe you can wipe out the password field, save the file, then reset the password using the passwd command - just press the enter key if prompted for the current password.
If this doesn't work, you didn't get this advice from me