I'm starting a playthrough of privateer, but without a joystick. Gameplay isn't so bad, but keyboard controls do "jump" a lot, which makes aiming a bit of a pain. Is there a way to have the keyboard arrows have both large jumps and small jumps? For example, does a patch exist that makes it possible for the [left arrow] to jump a lot, but then [Ctrl] + [left arrow] to jump only a little for fine-tune aiming?

If that is possible it should mention it in the manual or maybe they patched it in with an update and then it should be in the readme, but honestly I wouldn't know because I always played this with a joystick.

However you might want to use mousecontrol, you can finetune mouse sensitivity in the dosbox%.conf.
Use a real computermouse though, trackpads won't do you any good here.

Try mouse. Really. I played Priv in 1994 under DOS with keyboard and joystick (precision close to keyboard's). I was surprised that mouse control is far more better. Maybe it's matter of DOSBox.

I did. It's not as bad as I thought it would be. Took a bit of time to get used to it. Thanks for the recommendation!