Currently subaccounts can view logs and graphs of the master account. How can I create another admin in the event I need to add/remove/modify a monitor as well as create reports, read graphs and logs?
Creating a subaccount and sharing access to logs and graphs can only give you that. If a subaccount wants to see the actual monitors of the master account and make necessary changes, then that subaccount would need the master account to grant the login access.
What you need to do is log into the master account, on the left hand side of the menu, click on Share Access -> then click on Share access to log and graphs. From there you can grant accounts login access.
Once the access has been given, the subaccount can then login to his own account. On the main page (Dashboard menu item on the left), on the bottom left of the Dashboard, you will see the name of the master account you are allowed to log into. Click on the login link to login to the master account. You are not prompted for the master password, because a security token was already established when the subaccount user first logged into his own subaccount. So it is a one click login. You then have all access to the master account.