Congratulation for your fork, you've succeeded in improving state diagram result, which is not easy...
The main issue is that graphviz/dot is not adapted for state diagram.
We have started some time ago a try with another algorithm using this paper.
Here some input:
Here we are talking about BPMN but somehow the same algorithm could be used for state diagram.
As you see, This is really a preliminary version which is far from working.
Unfortunately, we are not working on this, due to lack of time.
However, the code is not that hard. Everything is in this package.
What I mean is, since you've forked our repo, you should have a look on this bpm package?
It's more complex than tweaking the actual state diagram but it could give far better result.