Why does ttf2afm crash on FontForge ttf files?
I don’t know. The ttf2afm that was distributed with my redhat 7.3 linux certainly did crash. When I downloaded the source from pdftex area of ctan and built it (with debug) the resultant program did not crash. Therefore I believe this is a bug in ttf2afm and that bug has been fixed. The afm files produced by ttf2afm don’t conform to Adobe’s specifications.