Hi 3am, thanks for your trying to reproduce, AND RESOLVING the problem!
I just tested the 1st point in a fresh aero.msstyle : icontitlefont:font does change the ProperTree fonts (+the address bar + the bottom panel + the library group headers + the explorer items). But, this is not important since what follows :I tried, according to your 1st point advice, to add a FONT:FONT property under Explorer & Shell > Explorer > TreeView. The result is :
Only the ProperTree font changed
The spacing between treeItems is conserved !!
Conclusion : as you mentioned it on your 2nd point, the font:font TreeView property bypass the font-dependent Items height given by the system metrics font size. Is there a "resolved" tag anywhere ?