Ooops, sorry. YOu need to drop into the monitor program first with the command sys 1024. That runs a little program called TIM which allows you to look at the processor registers and scan memory
So type
sys 1024, get the register display as you saw in post #29
then at the full stop prompt type
M A000 A080 and it should put some hex numbers on the screen. That is the contents of each memory location. We believe the ROM starts at A000 in hex and TIM understands HEX so its the easiest to use.
However what you posted above was interesting, it means that the sys command doesn't understand negative memory references so the sys 40960 is returning an error by attempting to run code from that point rather than the command itself not working, which is interesting.
It would be great if you knew someone locally who could read the ROM in a compatible programmer then send the file to us, is there anyone you know at all ?