Hi,
You can use another pool url, just use the same command and BFGMiner after installing that AMD APP SDK that I linked you to.
Multiminer is a noname application to me, I cannot help you fix your problem with it.
Give BFGMiner a try, use the same command as in the tutorial, just replace the link with the pools link and the username and password with your worker's username and password.
If this still doesn't work, I can try teamviewer with you for a few minutes to see if its an obvious problem.