Sorry, John. There's no way to do this with REPORT. Then nonbreaking spaces are deliberate. REPORT really wants each LINE statement to create exactly one line of output. Possibly you could post-process the RTF output but that's out of my league.
Although you cannot get rid of the unbreakable spaces inserted by proc Report, you can add your own breakable spaces where you think you should have some... Use ODS ESCAPECHAR="^" ; (for instance) and then the breakable space is ^w. Just add it in your code, something like :
description= Part1 || "^w" || Part2;
If you resize the table in the RTF document, that would cut the text between part1 and part2.