Every time i fasted or detoxed in any way - I experienced different reactions. It differs even more from person to person. So don't worry and just trust that the body knows what to do to heal.
I hope it won't be too uncomfortable for him:)
And great that you are pulling - it definitely improves the sleep.
I hope someone with asthma/allergies chimes in to give you more feedback on how oil pulling helped them - but please keep us informed of the progress.