Over-inking in highlights / curve starting points

Hi all,

I’m trying to get an unsupported film (Colourbyte) to work because pictorico and fixxons are too expensive to import and unavailable in the UK. Pictorico uised to be available through innova but they don’t have any at the moment.
Another alt process printer is using the Colourbyte film, albeit with Epson inks so it does work under those circumstances.

I am getting some over-inking in the highlights of my step chart. This can be noticed because the lines between boxes aren’t crisp/are bleeding. This doesn’t happen with fixxons of pictorico.
Clearly Colorbyte won’t take as much ink. However, the negatives I’ve printed that don’t have a pure white print absolutely fine so trying to find a work-around.

My questions are in PPE
Is there a way to lay down less ink and still get a paper white? i.e do I need the maximum inkload?
If I make the start point below 255 will I be introducing tone into my highlights?
What is the approach to modifying a curve I already have calibrated and is working well to reduce the ink in the highest values?