hmm, forget early startup menu. try using CTRL+D to break startup sequence and get into shell. or make boot floppy on other Amiga (you do have one?). hopefully FD0: has priority. sorry, I cant help you about commands, don't know them.
if you have other Amigas you could easily make sernet or parnet boot floppy that would allow access to dirs.
how come you don't have a520 modulator? its sooo easy to get secondhand a500 with a520 for few euros.
