In reply to OS X doesn't like my font:
Okay, that was no fun at all :-)
After checking virtually every single bit in my source TTX and going over every line of ftxvalidator output I finally nailed the problem. FYI, this was PICNIC ("Problem In Chair, Not In Computer").
It didn't help that ftxvalidator kept on telling me that a font with my Postscript name "is already installed". Running atsutil databases -removeUser a few times finally cleared that 'error', and only then something made me check the Postscript name in the 'name' table ... against the Postscript name in my CFF.
Duh. None of the tools I tried (Adobe's own AFDKO suite, Apple's Font SDK, Font Book, Linotype Font Explorer, and TTX itself) thought it worth mentioning. InDesign probably ditches the 'name' table as soon as it can and uses only the CFF data; or possibly it's smarter than your average bear (hold on, I'm gonna check what it says as "Postscript name" ... the one in the 'name' table! A small surprise here, it actually ignores the one in the CFF part.)
(Good news is I learned about twenty other possible issues with my home grown font creator. And of course I learned how to use the above-mentioned dozen or so tools.)