Watering plants in the coarse substrate that you have here is a bit different from normal potting soil. It hardly spreads the water in the substrate. So in order to get the whole rootbal moist, you need to use a watering can with a spray nozzle thingy. All the surface needs to b watered.
I have my ficus (still) outside in the gardem (Except for one I defoliated). They get rained upon every few days. THey do no tmind a lot of watering. THey do dislike continuous water-soaked roots. Water more frequently, give the tree more light (Late afternoon sun only untill there is a healthy crown of leaves). It should recover.