Hullo,I am far from being an expert on eorcism of demons,but please consider this statement of Jesus when the disciples were unable to remove a terrible spirit that afflicted a young boy at that time.
He himself called this spirit forth from the lad,but after when he was alone with his disciples he told them that this spirit could not be removed from the boy without much prayer and fasting.
Now it seems to me that it may be prudent to fast for this loved son.I am not sure how you would go about it,(wheather you should fast a set day for the time it takes,or a straight fast till the spirit looses its hold upon the soul of this person.)
My self i believe it would be wise to tell the boy that you will fast for him.I think it would be a very good idea for the whole family to fast together for him.(both those that are believers,and if willing those who are not.)perhaps there could be a certain day of the week in which you can take no nourishment for a set period.24hrs or sun set to sun set -sun up to sun down?
I think that this may help him to find his own self worth and your love at the same time.We seldom fast as much as we could .And Jesus instructions in the matter may be the key in reaching this person.
I am sure that he should be informed that it is being done though….with much love and respect for him….God Bless you in your abiding love for this wayward soul….b