FOr cod liver oil, use the amount recommended on the bottle (I am not at home. TOnight I will look at the amount of IU on my bottle and come back to you, in case yours does not specify how much one should take.)
Dry eyes is the liver struggling and that liver oil (vitamin A) will just do it.
I am more concerned with toxins in the food we eat than I am about finding some in the supplements.... in part because I NEVER go for the cheapy when I buy suppl., with the cheapest stuff I would be concerned with quality issue. Fish and seafood are very likely to contain heavy metal, unless they are deep sea animals (shell) so I tend to go for them preferably.
I drink 4 liters of water a day, I started doin so when I was sodium deficient, as soon as I increased the sodium intake (salt in drinking water) I did not feel thirsty all the time as the sodium help retain the water inside and it no longer passed through me. Yet I pretty much sticked to this quantity naturally. Simply because I drink lemonade (water lemon juice and cayenne pepper) in the morning until I get my first bowel movement.
As long as you drink according to your thirst, that is alright, although
drinking more (fasting) is a great way to help the critters out especially so along with psyllium husk.
However, if you have kidneys issues: lower back pain and swollen eyes, then you really should increase the water intake.