I'm not familiar with the afd debugger. What I can find appears to refer to a 16-bit tool. Unless there's a newer version, it isn't going to run on Mac, except in DosBox or something similar.
As for Nasm itself, what happens if you download the source and do "configure" and "make install"? Sorry to be so vague, but I've never run a Mac. Anything you can learn and post to help others will be appreciated.
Best,
Frank
