If your BB cannot send/receive PIN messages then it does not have a data plan. This is needed for and wireless activity like email to work.
I read your other post as well. The 2 items you mentioned are recommendations, RIM prefers the BES to be installed on a member server by itself.
One user means one user. The BES needs the BESAdmin acccount but only one BESAdmin account. You can have 500 users but you only have one account to manage/maintiain the BES.
You will not be able to pusd an apps wirelessly until you get a data plan. Once that is corrected check the BES Admin guide and the BES TKC, BlackBerry Technical Solution Center
. Lots of good info there.