Yes, your instructions work and I now have a standalone mode AP working on the Pi Zero W music player.
However, a question, I understood that on the Pi3 and Pi Zero W, the WiFi chip could act as an AP and connect to a WiFi router at the same time.
Is this the case and if so is it possible using the Max2Play plugin? (reason – one could then (when at a know Wifi Connection point) get internet radio. (obviously one would have to deselect the „standalone mode“).