Honestly then you are either going to have to resort to JS for this, or stick with fixed widths.
It’s extremely awkward as it is right now to give you what you want with just fixed widths, unless you do the column route (that’s what I first thought of when I read this thread)
Absolute positioning is extremely fragile and I’d shy away from it
Javascript is a bit overkill and I’d just stick to fixed widths for this