I thought those black things were scale and this was an impossible to treat scale infection. But when I put some hydrogen peroxide on the black areas, nothing happened. I then scraped them and it's just dead stem or buds. So, I decided harder to try and rescue the plant. I setup a nursery inside a tall glass vase, and at the bottom I placed some live sphagnum moss. On top of that I placed the pitiful remains of my moth orchid, and then I put the Spanish moss on top of that to maximise the benefit of the humidor. For extra humidification I placed the vase inside an empty aquarium and put aquarium water into the vase to provide some nutrition. These are the results a month later. You can see a new leaf (keiki) appearing at 7 pm on the stem! The other roots closest to the sphagnum moss have turned dark green.
Even the Spanish moss is enjoying the environment and has started to flower
So, with more time I hope to have saved this moth orchid.