#1 Login to your Database or PHPADMIN.#2 Go to members#3 Find your user account name#4 Set group Id to the admin group id. (Try 3 if you don't know it.)Or... ^ He beat me to it :s
Go to your ACP and enable the Registration Question and Answer Challenges.
Then I suggest you use an application which can be found on here called Stop Forum Spam.
Make sure to enable your captcha for signups too.
That should 99.9% stop all spammers! hope that helps
Bootstrap would be a nice framework to use in the theme. Also include some sliders like the Facebook app. There's tons of jquery plugins out there for this.