You may need to drop into plain PDFLib to do this, IIRC the latest version supports a table-type layout, not sure how much automatic formatting it will do for you. You can always concat two (or more) PDFs using CAM::PDF if you find that you need to generate them seperately.

How can I translate this to textbox width?

PDFLib supplies a way to get the width of a given string using the currently selected font, I don't recall the function name right now, but it should be easy enough to find looking at the manual.