I haven't test my patched 86dos.sys 1.10 further, may do it later.
and for QEMU's monitor output, I think it is linear format (since I'm using $pc, not $cs:$ip)
and I think it is valid x86 code
for no.3, PC DOS 1.00 doesn't boot, but it doesn't have a tight loop in low address, it stalls at...