Recently I rewrote the code. It has become a bit faster. Most of all, it has become more easy to add new pieces because it is configurable where it concerns movement and capture. For example, adding Hunter, Archbishop and Chancellor was a 30 minutes job, no coding effort involved.
What is the next piece that I should implement?
I don't think Black's f pawn value is the only or biggest issue.
In the 1st position of post #22...
If Black is anything close to even in evaluation, there's something seriously wrong. My guess, the Witch.
Try removing the Witch from the board and see if that helps.