For your 1st problem:

Have you installed phpMyadmin? If not, you should, as it can make user-management for your databases much easier.

sudo apt-get install phpmyadmin

Once you have that installed, post back if you need help setting up users.

You do not want to use user "root" for much of anything. In fact, I usually create a new user for each server I work on, and name it something that matches that particular server so I can remember (for example): server11_admin

then I give that user all the global privileges (including grant)...log out...log back in with that new user, and test that I have full privileges by creating a database, creating some sub-users, etc.

and then (and only then), if everything is good, I delete "root" completely.

The reason: bots and such will try to log in first with "root" as it is a default name.

Also, as you are creating new users, be sure to use strong passwords. I like to use this:
http://strongpasswordgenerator.com/ to generate good random passwords.

For problem2, someone else will have to chime in, as I shy away from cache applications since most of the sites I work with are smaller (less traffic) sites.