For edibility, you can use -300 to make it inedible, -299 to -1 to reduce health/energy (poisonous), and 0 will be edible but do nothing. All positive values add health/energy! Although the math is hella weird and is not really understandable. The
official wiki (in the Modding:Objects section) has the maths necesary to calculate edibility.
The recipe tutorial from the
stardewmodding wiki will help you a lot, although they reference an official wiki template for edibility that doesn't seem to exist anymore... sorry about that :(
You can check the
official documentation for Content Patcher for more help with how to set up correctly the EditData part of your food objects in your content.json! What you need is on the "Edit a dictionary" part.
Hope it helps!