Hi Andrew,
I would be happy to help you, if I only understood what you meant with "the pedal-sweet spot for the half open hihat is way too small".
Is the volume of the half-open hihat sounds too small? In that case, yes, with DSoundTool you can increase the volume of those sounds.
But if the problem is that the distance between fully open and fully closed is too small, I think you should try to calibrate the hihat to use a bigger distance (you have OS 1.10 installed, have you?).
Best regards,
Louis