Again, the cooking System itself is nice, its just overloaded with Information, and the Nutrition Stuff is in my Opinion rather dumb. But not the cooking itself.
As a hacky example, you could just give all Things the same Nutritional Value for all Alpha to Zeta Things, and then hide their Display in the UI. Should require little work, and keep the cooking System as it is basically intact. Then its all about the Presentation really, so you don't have various Graphs for the Flavors, and all that many Numbers that makes it look like a Spreadsheet, but a more game-y and comfy looking Interface.
As for Interaction, I think you're probably tracing a line from the Camera to the Crosshair anyway, if you'd just reduce the Distance a bit, and have it check for no collision, you should be fine. That way you can't interact with Things through Walls, and not over 20-30m. But I don't know how easy this is in Unity.
I just quickly googled it, and I know not enough about Unity, but did you mark the Meshes as static? Are you batching and reusing your Materials properly? Is your Shader for generic fully opaque Meshes complex at all? Sorry, probably not very helpful, but from what I gather Unity should be able to easily handle thousands of static Meshes, so the Error must lie somewhere else in there, thats just tied more secondarily to the Meshes themselves.