[ODE] How to make simulation look more realistic (fast, in look)?

[michael kapelko]

If I have gravity of -2.5 and step 0.05, simulation is really slow (not 
in performance, but in look).
If I make step equal to 0.5, all's incorrect. If I increase gravity 
(-50), my wall crashes and nothing can really fly.
And when I move player capsule with -2.5 gravity, it doesn't fall fast 
enough on stairs, it hovers too much, because I apply force so that 
player movement looks like in real games.
So how to make simulation much faster? So that objects fall fast enough, 
player moves fast enough and falls on all stairs when climbing down?
Thanks.