Well - you are in a bit of a bind here; and 'twas ever thus. We are told that God is on both sides in a war (e.g. the Germans believed this and so did the Allies). The interpretation of his/her purposes has been a conundrum since time began, as people of all faiths believe that the "message" they are receiving is the right one, even though it contradicts that of others of equal but different (or as in this case the same) faith.
If scripture is your guide, then it is a problem as the bible has so many contradictions and both you and your son could search and find quotes to back up your arguments and positions. That is not a very productive or constructive route.
It seems to me that the way forward is not to allow your sustaining faith to flag, but to take a broader view of your deity and his/her purpose. Just be motivated by love and kindness and use this as your route forward. This will probably involve acknowledging your son's interpretation of the way forward as valid and to be respected, even if you cannot share it. This leaves him free to act as he sees right and you to do the same without argument or strife, or a weakening of your position.
You do not have to doubt your own belief - you just have to recognise that all faith and belief is open to individual interpretation and always has been.
Having this faith is clearly important to you, and, although I do not share this in any way, I do recognise your dilemma and hope that you can resolve this in a way that leaves you at peace with yourself and with your son. Part of the art of being human is to be able to acknowledge different views and to take those into account without losing faith in one's own.
I wish you well with this. 