How much filler is completely dependent on the patient and injector, but it is good you started slow and can build rather than putting too much in!
You likely need at least 1-2 syringes per side more in the midface area.
However, for longer-lasting results, facial fat grafting may be a good...
For unique cases where a variety of modalities could be used to treat the condition, I would suggest an in person or virtual consultation to develop a custom and effective treatment plan. It is difficult to precisely define the best option without collecting the same information. I suggest...
It will fade more with time. An IPL laser would help resolve it faster and you would likely only require one or two treatments. I would highly recommend diligent sun protection to prevent further pigmentation. Some people have success lightening the discolored skin with the use of prescription...