nobody so far has answered your question about the "nobody" user....here goes:
when top lists the username 'nobody', it has NOTHING at all to do with which user is logged in to your web site.
top doesn't know, doesn't care, and has no access to details about your web site or the user accounts it has. top displays details about running unix processes, including which unix user id (uid) each process is running as.
i.e. the 'nobody' mentioned by top is the Unix user which is running the apache process.
presumably your system is configured to run apache as user nobody as that is a minimal priviledge account which can't do much even if someone manages to compromise the apache program. this is quite normal. some systems run apache as user "apache", "httpd", "www-data", or some other username but running it as "nobody" is fine...it's just another unix user on the system.
unless you're using suexec or similar, all apache processes will be running as 'nobody', regardless of who happens to be logged in on your web site. since you're asking questions about who the nobody user is, i think it's safe to guess that you're not running suexec.
to summarise: it's NOT a problem and doesn't need to be worked around.