So if a DAW only does 7-bit (128 level) MIDI i/o, it’s kinda built-in that the stair steps are larger. The steps with 7-bits are 128 times the size of a 14-bit step.
But given this is a Hydrasynth there are things that could be done to help. For instance you could assign a Macro that sits between your DAW and the value you want to tweak, and setup a sub-range of values for the output of that Macro. The Macro takes a MIDI CC value in. You won’t be able to sweep a larger range, but perhaps that’s a useful exchange for you. I haven’t tried this to be sure this would work, but i think it will.
So is this more a question about your DAW — Bitwig in this case. I don’t use Bitwig, but a quick search seems to indicate that indeed it lacks an NRPN interface. Perhaps there are answers in a Bitwig thread ?