Does mercury fulminate really look like crystal methamphetamine?
Mercury fulminate $\ce{[Hg(CNO)2]}$ can have a white, gray or greenish-brown color depending upon purity and dryness (it is often kept moistened to prevent accidental decomposition).  


  Does fulminated mercury really have the translucent white/blue crystal
  appearance as was shown in this scene?


I've never seen a picture where it appears translucent or where it has a bluish color.  The pictures I've seen always show it as an opaque powder.  I suspect that it could be crystallized, but that's probably never done as it would further increase its sensitivity to detonation (e.g. if a crystal cracked, or rubbed against another crystal, the friction, triboelectrification, etc. could cause the material to explode).  Here are some pictures.








  Is the compound that sensitive that throwing it against the wall would
  cause detonation?


Here is a link to an examination of the Breaking Bad "detonation by throwing" experiment (with video).  The conclusion is that it can detonate when thrown, but 1) a larger amount of material than what Walt had, and 2) a much harder throw (greater force, greater shock) would have been required to cause detonation.