Agree about the case when APS fails to operate. There were emergency procedures that involved disassembling some part of it and directly wiring a power connection to the oxidizer and propellant valves. See the end of https://www.hq.nasa.gov/alsj/LM11HandbookVol2.pdf

I think the latter scenario is virtually impossible: the ascent stage didn't have any landing gear and the engine wasn't throttlable, so even a relatively soft landing with fully operational APS would be impossible.