If he has a wheeze- he might wake up with a cough
and difficulty in breathing.
But 2 hourly nebulisations will help him out.
Hope he is on oral broncho-dilators too.
Since sleep is much disturbed, its better that you take him to ER. In severe cases of wheeze, short course of steroids
can be given which will give him good relief.
Nebulisations have to be continued. Please check if technique is right, the equipment is good and white fumes are generated enough.
Hope my answer helps you.
Wish your son a speedy recovery.