Unfortunately, no working Mac emulator can run A/UX. It's remotely possible MESS might hit that point eventually, but they're not there yet. BasiliskII and vMac "cheat" by patching the Macintosh ROM to fake certain hardware devices, which doesn't work with software that needs to hit the bare hardware like A/UX does.

I do wonder if it might be possible to copy the contents of that boot floppy onto a hard disk partition, boot from that, and then install A/UX normally via the CD-ROM. I no longer have the means to investigate that possibility.