i didnt see a point for the enable/disable, so you can make it all 1 text event:

on *:TEXT:!8b *:%chan: {
  if ($2 == on && $nick isop # && !%8ball) {
    /set %8ballg $2 | /msg $chan 8Ball enabled.
  }
  if ($2 == off && $nick isop # && %8ball) {
    /unset %8ballg | /msg $chan 8Ball disabled.
  }
  if (%8ballg == on) {
    set %answer $rand(1,10)
    if (%answer == 1) { msg $chan %8ball Yes }
    if (%answer == 2) { msg $chan %8ball No }
    if (%answer == 3) { msg $chan %8ball Maybe }
    if (%answer == 4) { msg $chan %8ball Of course! }
    if (%answer == 5) { msg $chan %8ball never }
    if (%answer == 6) { msg $chan %8ball keep dreaming }
    if (%answer == 7) { msg $chan %8ball Yeah right.. }
    if (%answer == 8) { msg $chan %8ball And our survey says... | .timer 1 2 /msg $chan \"UH UH\" NOPE! }
    if (%answer == 9) { msg $chan %8ball And our survey says... | .timer 1 2 /msg $chan \"DING\" Yup }
    if (%answer == 10) { msg $chan %8ball Maybe if u keep dreaming. }
  }
}