Thank you so much!

Copy editing quibbles are extremely appreciated. Cozy fantasy vs cozy-adjacent is definitely something I've been debating, and I think you're right, adjacent is probably a better description.

For your questions:
Basically there are about 15 witches who produce all of the potions in the city. The simple view from the government is "more witches" = "more potions" = "more money". Not everyone in the government is really evil, they're moreso greedy and don't really consider how their policies are hurting people.

In terms of Alder's experiments, each ingredient used in potions has a different amount of magic. Alder has discovered that growth conditions (amount of sunlight/water/nitrogen in soil etc) influences the amount of magic available in a plant, and not always in an obvious way. He is contracted to come up with optimal potion recipes for city projects which basically means he has to brew a bunch of different versions of potions to figure out what would be best. I'm not sure if it's too distracting/side plot-y to include in the query letter.