Two things to pay attention to. I would really try hard to get rid of the scale. I have been fighting some for a while and just when I think I am rid of them a new crop pops up.
It's in a huge clay pot with drainage (has a catch plate so I can see when water has come through)
It's possible that you are not thoroughly wetting the entire root mass. I know that it is difficult to water a large plant indoors without making a mess. The thing is if you water until a little water comes out then I suspect that parts of it are remaining dry.
I tend to give it enough to run through maybe twice a week.
Unless it is in a very free draining, bonsai type mix, which I doubt, I would think that it would not need to be watered so often. This also leads me to think that you are not effectively wetting the soil. A large pot like that, if watered properly, would probably remain moist for more than 3 or 4 days.
If possible take it outside or put it in the tub to water is very well once and see if it makes any improvement. Water the entire surface of the soil until water runs freely. Wait 10 minutes or so and repeat this. Do this several times until you are sure that the entire root mass is thoroughly wet.