Makeshiftwings - welcome to the forum.
These days my gardening and plant growing is mostly outside. When I was young, single and living in an apartment - no yard - I grew a wide variety of foliage plants and vegetables either in my apartment or on the balcony. My apartment an balcony resembled a small tropical jungle.
My first ficus gave me fits. I was growing a Ficus Benjamin. Yours is an Amstel King. A different variety but it has the same growing requirements.
I spent a good bit of my hard earned money on a lovely, braided ficus. I did some research - at the library. The internet had not even been thought of yet. In fact there was no such thing as desk top computers or home computers. This was the era of punched cards, paper tape and magnetic reels. Bill Gates was still working on his ideas in his garage.
Got off track.
I had a sliding glass door to my patio that faced ESE. I placed my lovely ficus to the side of the slider, watered it, misted it, fed it. It lost every leaf!
Several problems -
#1 - I had changed it's environment. Ficus do not like environmental changes.
#2 - it was getting a draft from the A/C vent.
#3 - it was too cold because of the A/C vent.
#4 - it was not getting enough humidity
Ok - you can not do anything about the environmental change. Give it a home an leave it there. Make sure it is not getting a draft from either an A/C or heater vent. It needs light but you do not want it too close to the window especially during the winter. Because my plant was to the side of the slider I had to turn it weekly to keep it from growing in one direction.
This is one of the very few/only times you will hear me advocate using a pot saucer. My plant was in a 16" pot. I used a 24" pot saucer on a wheeled dolly. Fill the saucer with pea gravel. Set your pot on the gravel. Put water in the saucer but not so much that the pot is sitting in water. This adds humidity. Keep the soil in the pot evenly moist - just damp - never soggy. Wheel your dolly to a watering spot. Remove the pot and water it. Allow it to drain before returning it to its home. Keep water in the saucer and mist your plant twice daily. NEVER use Leaf Shine. That puts oil on the leaves that blocks moisture absorption and collects dust. Fertilize with a liquid or water soluble all purpose fertilizer once a month during the growing season. Let it rest over winter.
I did not see where you are located. In Lafayette, LA. we are blessed with extremely responsive County Agents. Unfortunately that is not the case in all regions. You can try giving your County Agent a call or even contacting your local Master Gardener Association. Pathogen test (disease or insect) are usually free through your County Extension Office.
It is difficult to judge but your pot looks too small for the plant. Transplant to a larger pot - 14" to 16". Don't panic when it looses leaves after the transplant. Allow 1" from the soil level to the top of the pot. Do not plant your ficus any deeper than it is currently planted. Loosen the roots before planting.
What I would do:
Bring a leaf sample to my County Agent
Pot up to a larger pot
Position the plant on a gravel saucer in an east facing window but not right next to the window. No drafts
Maintain a day time temperature of 70 to 75 degrees and no lower than 60 to 65 degrees at night
Mist twice daily
Once you have done these things - just give it regular maintenance. Your plant WILL loose leaves due to the change.
BTW - the leaf sample to your County Agent is a must do.