Have you checked IOSPE?
It doesn't answer all your questions but may help shed some light.
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This is a discussion on Aspasi lunata seedling, dropping leaves within the New Growers: Ask the Senior Members forums, part of the New Growers category; I bought a seedling Aspasia lunata about six months ago. It appeared pretty healthy, and ...
I bought a seedling Aspasia lunata about six months ago. It appeared pretty healthy, and even grew a new pseudobulb. However, a couple of months ago, the leaves started to fall off starting witht the smallest, oldest growth. Now, only the newest largest pseudobulb has leaves. The leaves did not appear burnt, or damaged by insects of fungus. They just turned yellow, then brown, and fell off. In addition to this, it has a new pseudobulb that is growing very slowly. It's about two months old, and only about 1/2 inch long. This orchid is planted in a 2 1/2 inch pot with fine fir bark. It gets medium light from my east-facing window. Humidity usually stays above 50% around my windowsill. Temps in the mid 80s or lower.
Terp, that page didn't have much info about culture, other than to say that they were hot to cool growing. I guess that just means that they have a wide temperature tolerance. After a google image search, it appears that a lot of healthy looking plants have leafless older pseudobulbs. Maybe this is just normal for this species? The pseudobulbs on my plants aren't shriveling and dying, just dropping leaves. I believe this plant is in the Oncidium alliance, and if I'm not mistaken, there are other orchids in this group that will eventually drop the leaves on their backbulbs.