It could be the zone your in is too cold for your fig. Or it is in the open with no protection and the wind if freezing the branchs. Try using a tarp over the fig tree. If it dies back every year it shouldn't be that big. Put fresh compost around the base in december. The heat from the compost will help keep the air traped by the tarp warmer than out side. Or find a protected spot and transplant.