I used to have issues growing
ficus until the plant guy who vistied the office clued me in. Since yours has been in the same location for 3 years, light doesn't appear to be an issue. Although they don't usually like much direct light, especially hot afternoon sunligt.
A previous post suggested; and, I agree, to water only once a week. Just enough to moisten the soil, but not soaked. The best way I figured to explain it would be to soak a sponge in a bucket then wring it out, and that's about the proper dampness for the soil. Be sure the pot isn't sitting in water as they don't do well with "trench foot". Putting the pot in a saucer with some pea gravel or aquarium gravel to keep its feet dry will help. I'd also use a balanced fertilizer once a month during the growing
I also agree it looks like it's time to repot. I would go one size lager than it's in now. As for a potting mixture, I had very good results using a plain potting soil from Home Depot's nursery center. To 3-4 parts potting soil I added 1 part houseplant peat moss and 1 part sand. This will give good drainage and retain some moisture as well.
The above were used on a ficus I had for over 4 years, which I had to give away when I moved cross country in the dead of winter. In that time it did very well and I hated to part with it. One other thing I did was rotate it 180 degrees once a month.