How do I force password reset even with wrong password entered?

I don’t believe there is anyway to migrate passwords from our current
site due to encryption.

I wouldn’t necessarily rule that out. While WP uses PHPass as its regular hash for passwords, it still supports MD5 which was the original hash.

If a password is an MD5 hash, it will be updated to the new hash when the user logs in.

If your existing site’s passwords are MD5 hashed, or if they can be converted to MD5, then you may be able to migrate your passwords.