I would recommend looking directly at the condition of the roots. An d then perhaps cutting all the dead ones of and repotting with lava as grit possibly around 50%

You are bringing a old thread up. OP has got his answers from the experinced users in here. OP is probably long gone and will not see your post anyway.

Your advice could actually harm the tree more than it is. You don't repot trees and prune roots at this time of year. Especially not ficus.