You are going to need to fire up a Live Session and chroot into your install to do anything in package management or even creating files in your install.
Once you have mounted the install on the Live Session you will be able to access the file system by opening the file manager as root.
Next time you want to experiment with system files don't remove the buggers. Simply rename them. /etc/passwd would become, as an example, /etc/passwd.def. The suffix you decide on can be anything you like. A lot of people like .bak. Windows users like .old. I like .def (default) for experimenting.
I would try, in the chroot environment simply running;
Pretty sure you will have problems with this. The errors will point you in the direction you need to go.
In chroot you should have no trouble installing packages unless you have broken some link that affects dpkg.
Another thing you might want to try is;
Code:
dpkg configure base-passwd
or maybe it should be;
Code:
dpkg-reconfigure base-password
The idea is to get the install script for that package rerun to correct your "improvements".
A simple;
Code:
apt-get install --reinstall base-password
may do the trick.
Hopefully the system still will recognize your user. This seems a bigger concern to me than the password for root. root is, just like your user, a recognized user of the system. Problem is root is the only user that is common to all systems. Your user name is not.
You are, I am sure, going to have to run;
Code:
passwd <your user name>
if that runs it will be great. Problem is your group information may be gone too. May not be though. If not you should be fine. Check to see if /etc/group still exists. If so you should be alright once you get base-passwd to be reconfigured by the install script.