Dark Matter

Am I correct to assume that the amount of dark matter believed to be
seen in the local galaxy is way way too much to be accounted for as
simply ordinary matter which is also dark, but must be some new kind
of matter which we simply do not understand on any level?

Also it seems to me that this dark matter would have to not effect
photons at all, thus it is dark.  This, I imagine, must mean that it
is smaller than any existing quark.  Is this correct or ignorant?