I have collected 3 fixes plus one experimental change to KindleUnpack and attached them here.
kindleunpack.py - fix for multiprocessing on Windows
mobi_opf.py - all fixes to date plus hopefully all xmlescape
and unescape changes needed
mobi_split.py - fix for KindlePreviewer 2.8 and split mobi 7 files plus
an experimental fix to replace fonts with 0 size sections
All 3 can be found in the attached zip. I would appreciate hearing of any successes or failures.