Yes – I’m not sure what’s happening to the ISO and the F-number in dcraw. There must be some kind of bug/shortcoming when reading DNG images. The fix is to add the following to the setting of the “@exiftags” array in the raw2hdr Perl script:
-ISO -ApertureValue>FNumber
You can edit the script in a text editor. I tried it and it seems to work for your image.