Ficus Ginseng - Rapid Leaf Fall/Dying/Yellowing

Please help! 

I've had this one for around 5 years, it has been happy, healthy, dark green until a few months ago, when it started getting some yellow leaves and some leaf drop. It's worth noting that nothing changed in the care of this plant. 

Then over the last month or so, the drop sped up significantly.
I reached out to a gardening group, where they suggested checking the roots, re-potting, a UV grow light and fertilising. 

I removed the plant from the pot and found a white mould/fungal kind of situation all over the roots. I fully cleaned the root ball, did a peroxide soak (1:9 with 3% peroxide), rinsed with fresh water and let it dry. Then re potted and watered with some additives (Growth Technology Silica and Foliage Focus).
I have been making sure to wait for the soil to dry before watering each time. I also installed a UV grow light and have been having that on for 9 hours a day. This was all about 5 days ago.

Since then, each day I check the plant & it looks less and less  and less healthy.
It now has brown leaves as well - this is new.

I'm having trouble getting the pictures attached, but will try to add to the thread.

I desperately need advice!
Should I prune it back fairly hard?
Should I cut off some of the thick trunks that feel hollow (not wet/squishy hollow, they feel dry and hollow)?
Should I just leave it, keep up with watering and hope for the best?
What should I do next? Does this plant have a chance of survival?
 

Do nothing more! This tree has already Been abused enought.

No pruning, no fertilizing. Just keep watering and hope that it recovers.