Thank YOU for playing through, and for the positive words regarding the scenes and world-building! T'is a pleasure to know there are folks who enjoy both sides of the game~.
As for your question, the moondust can be synthesized into an item with three units... and with a certain cauldron, yes.
There's a merchant on the other side of the slug den. Go all the way through, instead of heading down. He's waiting on the opposite side, and he'll give you the cauldron you need! You can still make something with the moondust and with other ingredients, so I recommend picking it up even if you missed it during the main game!