It sounds to me that the reason you have improvements with the malic acid is that you may have candida. I have those same symptoms with my candida, including the vision and sinus issues. I have found that as I get a handle on my candida, my vision clears quite a bit, to the point where I don't even need my glasses, and when it gets more out of control my vision blurs again. My mind is also clearer with candida control, and I tend to be able, even driven, to get more organized. Even if you don't get or haven't recently had a 'yeast infection' you could still have the worse version, systemic candida. Actually this is probably the most likely considering your symptoms. Like me, it has left the confines of the genital/gastrointestinal tract, and has moved up. Actually, it often moves up the GI tract into the throat and mouth(is the back of your tongue coated with white in the AM or during the day?) and from there can make a beeline to the sinuses which touches the ear and eye areas. Some people even get dizzy spells during a major candida overgrowth. Malic acid is used in many candida protocols. You may also find some benefit in trying the trace mineral molybdenum in conjunction with a good multi. The molybdenum helps break down the candida toxins to a form that is useable and removable by the body which affects the mental clarity issue a lot.
But don't take this to mean that you shouldn't flush, actually you may want to focus on some thorough bowel cleansing first, that will help make way for a future flush while also evicting many of the unwanted candida and their breeding grounds. The Liver Flush
will help your natural detox system get back up to normal which will allow your body to balance enough to get rid of the candida more efficiently with or without additional treatment.
Look into it, I hope it helps.