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Firstly , it is not necessary to pour any oil into ear , as ear has the capacity to produce the wax needed.
Secondly , this oil must have caused a damage to eardrum
and middle ear.
I will answer your questions now :
1)Even if eardrum is not ruptured , swelling of eardrum can effect middle ear.It could be possible that this swelling can be due to damage in middle ear.
2)Since there is not perforation , you have got a better diagnosis.There could be possibility that your ear parts had heat trauma and the recovery varies with other associated condition.
I advise you to visit a Higher center and get evaluated thoroughly .As you have been suffering for the past 3 months , Surgical option can be thought of based on investigations.