I suspect you could use CSS and line-height in some way with a calculation, but I never tried.
One way to improve results is to not cram massive amounts of text into a single field in the first place. FileMaker is not a desktop publishing system nor is it a word processor. It does have limitations.
If you can set up a list view where the data in a given record contains a portion of the text you now are attempting to fit into a single field, you may gain options you don't have with that approach.
Or you may need to use different software to produce the final version of what you want to produce here. If it works to manage the original data in FileMaker, you might export the data from FileMaker into a file that can then be used with another program in order to produce the desired reports.
No, not yet AFAIK - there are feature requests for getting access to styles via conditional formatting, what could help here as well