Thanks Helen/speakingtohe, it's amazing how well that works. I was able to remove "font-size" and "line-height" from "Other CSS Properties" and was able to adjust both line height and font size, and the final epub displays much nicer on the Mini.
I did check the font box in "filter style information" in the last pass into epub. Don't know if that was needed. Also, I added all the Kobo/Mini specific changes on the mobi to epub pass and not on the original epub to mobi pass. Is that the best way to do the conversion?
Thank again. I'm off to play with some of the other files that had line spacing problems.