Oh wow, this is really one of the most inefficient uv maps i've seen in a long time. Most everything here can be done with tiling textures, a good AO bake on a 2nd uv channel, and some decals for unique damage.
Justin Meisse has just produced a great example of how stairs in pretty much every game I can think of have been textured. It's a very optimal, quick and sensible workflow. Unless you need crazily unique / destroyed stairs, then this method is certainly the one to use. In general my main crit is the same as what the others…
Alright now things are starting to shape up, nice improvements =) As for the grime, now that you're doing it in tiles it does get a lot trickier, but not impossible. Its a good idea to leave leave the grime that will be repeated often out of the diffuse. Instead do a few grime/slime trails on a strip a lot like the stairs…