To get sharp shadows you have to lower the shadow distance parameter in the ini. But it has the drawback that only very near objects cast shadows. It seems that a shadow texture is generated in relation of your actual position. The shadow distance is the parameter how much of you surroundings are put into the shadow map. So you also have to higher the resolution. But i fear that there is a hardcoded cap or the other thing could be that the texture memory will too high.
It's called Cascaded Shadow Maps.
And no. Without access to shader code there can't be done much about it.
It essentialy works like this:
Number of shadows cascades * distance of transition
So. The more cascades you have the better shadows are... BUT high distance make shadows more noisy/blurred so you have to increase shadows resolution and number of cascades. But going anywhere above 8 cascades is going to kill performance anyway.