If you have a dedicated server (as you say) you should be able to manage it by editing your php.ini file to enable
proc_open. Look for
disable_functions = line (or
Anyway, correct way of launching setup.sh is
sh ./setup.sh. If you have a dedicated server you can create new users (other than root), give them proper rights and run under that user I guess to avoid the warnings?
Ctrl+C is way to abort any script right away.