First some basics: while that doc who told you single vitamin c is an oxidant is technically true, it's not the whole story. c is first metabolized to a pro-oxidant molecule in the body, but then after it acts as an anti-oxidant.
if the body stores of E a fat soluble vitamin antioxidant are adequate, it steps in as an intermediary to put C back into its antiox form.
the way around that has been known for decades, & that is why u usually see C paired with E and even A (as A C E) in a supplement bottle.
have u had a pyrroles test done at any time to find out if you're pyrroluric?
The eyes to function preferentially need/use ZINC more than any other nutrient, so i note here you are on the pyroluria forum, which is caused by mainly a zinc deficiency, being depleted due to its combining with excess created pyrroles in the blood.
your visual problems just might be a symptom of a zinc deficiency?
you have to ensure the fish oils u use are high quality; many are highly oxidised (rancid= fishy smell) garbage, so u must ensure again that you at least take an E supplement.
the peroxides in bad oxidised oils are bad from any source, including any/all fried or deep fried foods.
the brain fog could be many things: excess ammonia waste not converting to urea, it could be a defect or blockage (toxins) in the methylation cycle somewhere, or in the folate cycle which is closely beside:
http://vas.sagepub.com/content/20/2/88/F1.large.jpg
not shown well or in detail that diagram, look at "B12" & "ATP" where they are-- B12 actually has TWO active forms in the body, both operate nearly independently in different ways & systems!
u need methylcobalamin B12 for the CNS/nerves/spinal fluid, but you need the other active one, adenosylcobalamin, to run the mitochondria, which are the resident energy plants that churn out the critical ATP used everywhere.
if they are plugged with toxins, they drop to extreme poor efficiency, putting out only 2 ATP per cycle ANAEROBICALLY, instead of 38 ATP output per cycle AEROBICALLY.
So of course near zero energy to run the body's cells, & extreme physical fatigue. since the brain uses such a huge % of the body's energy, a shortage there is brain fog.
nerves will have pain symptom if energy is low.
both available as separate sublingual supplements; B12 "shots" or needles have been available for decades. but first u have to determine if that area is your problem.
http://www.wisegeek.com/what-is-adenosylcobalamin.htm
go here & look at the LH side 9 panels of grey pattern lines-- if u can't see at least 7 of the 9, u have VCS which means u have toxins blocking the visual processing cells somewhere, either in the eye or at the visual processing waystation enroute from the retinal nerve to the brain.
http://www.biotoxin.info/