Why are the acidities for H-CH3 and H-OH so different?
As far as the acidity of water goes, It is a very special case that observes the process of homoassociation. This is when an acid forms stabilizing hydrogen-bonds with it's conjugate base This allows water to be the more stable acid, because hydrogen bonds are observed between $\ce{OH-}$ and $\ce{H2O}$, while none are observed between $\ce{CH3-}$ and $\ce{CH4}$
This factor might not be significant enough to provide explanation for all of the difference that you are seeing, so there is still another culprit out there.