The $25 supports getting the fish to 3rd worlders at a low cost, http://www.luckyironfish.com. Far as I can tell the fish doesn't work if the water is contaminated with arsenic and/or manganese, so more research is needed.
No, it doesn't mean that at all. The authors in the paper you quote write about the possibility of iron sequestration due to arsenic and manganese contamination in the water during the second half of the study. They call for additional research.
Part of a series of FP lectures using Haskell. I was impressed by Erik's love for the subject. See 27:35 to see how Haskell boils down function composition to its essence, compared to C#/Java.