Your husband is signified by Jupiter, located in the 8th house of proceeds (like money) from a marriage. I think he is all about the money. But Jupiter is not in a strong position in the 8th house and in Capricorn, the sign of its fall.
With Gemini on the cusp of the first house (you) and Virgo on the 5th house of children, both you and your son are signified by Mercury. Venus is a co-significator for your child. The sun is normally a planetary symbol of one's husband.
You are in a slightly stronger position. Mercury is in its own triplicity and sect, and in a better house.
Mercury is retrograde, turning away from the sun. I don't think your son wants to live with his dad.
Beyond that, I am not seeing a clear resolution to the issue, just a lot of anger and stress, with Mercury retrograde applying to a square with Saturn, and the moon applying to a conjunction with Mars. My best guess is that a judge would ask you and your husband to save expensive court costs, and reach some kind of settlement, due to neither side being entirely in the right, but it won't be what either of you wants.
Obviously the real decision should rest with what's best for your child.
I'm sorry that I don't see a clear-cut win for either party.
Hopefully a better horary astrologer than I am will pick up on this thread.