Ubuntu – Can’t I type the password after using a sudo command?

That wont fly... you need a password for the sudo user to be able to disable the sudo password. So that goes the other way round: 1st disable sudo pwd then disabled-password. And I suggest NEVER to do this kind of action w/o a backup sudo user. Leave the 1st sudo user as is. Maybe with a good password (64 chars you generate randomly and store that in an safe). Use a 2nd sudo account to set your method up. That way you can use your 1st sudoer as a fallback.

And you need

{user} ALL=(ALL) NOPASSWD:ALL 

in

/etc/sudoers.d/{user}

If you can't un-disable you can use live session to edit the sudoers file.