The problem is that you're setting %flood whenever anybody says anything in a channel. You need to put set -u5 %flood On inside your if statements like this:

Code:
on *:text:*:#mychan: {
  if (%flood) { return }
  if ($nick isvoice $chan) || ($nick ishop $chan) || ($nick isop $chan) {
    if ($1 == .vent) || ($1 == !vent) { 
      set -u5 %flood on 
      .notice $nick 4Host/Ip:4 ***************1 4Port number:1 ****1
    }
    elseif ($1 == @vent) {
      set -u5 %flood on
      msg $chan 4Host/Ip: *************** 4Port number:1 ****
    }
  }
}