I am an ENT Specialist
having more then 15 years experience.
Regarding your first question, there is no medicine that can remove Adenoids
or make it less susseptible for any infection. So, best way is to remove it out . Removal will relieve nasal obstruction
and as there is no adenoid after removal, there will be no infection in adenoid! Regarding second question, no bad habit can cause enlagement of adenoids. it is due to low resistence power of the body against any infection. Give good nutritius food including fruits reach in vitamin C
. Regarding third question, one X-Ray will not cause any harm. Repeated x-rays may cause harm. So, dont worry . I hope now you are relaxed! Have a speedy recovery of your son.