The vast majority of every food web you have ever seen is only a tiny fraction of the real food web for that ecosystem. Most environments have a large number of species in their ecosystems, especially the further down the pyramid you go, you should have dozens of fish for instance, although it is perfectly fine for a few to dominate. A complete food web for any ecosystem is a densely packed interconnected mess, so unless you really want to you don't need to exhaustive. Also its not uncommon to just see something listed as (detritivores) or (marine invertebrates) listing every single species that makes up zooplankton for instance will be pointless for you.
One thing you should ask yourself is, "is my environment created by non-biological feature or some unique producer" examples of one created by a particular producer; mangrove swamps, grasslands, redwood forests, sargasso, coral reefs. Examples of ones created by something else; Fire-forests, flood plains, mountains, deserts, they are not mutually exclusive but it can help you frame your ecosystem in your mind. What foundation makes your ecosystem unique.
Grain and berries are also producers, they are plants.
insects and other detritivores will eat fungus ans well as most everything else. Many live off leaf litter. arthropods, shellfish, and fungi dominate on earth.
Keep in mind an animals growth cycle can effect what it eats, the young of an animal may eat something different than what it eats as an adult, young alligators eat primarily shellfish and insects while adults live off fish, birds, and mammals. So your Zhushe may be fine.
There are often many steps in the size of organisms, I don't know what size your hawks are but if they similar to earth hawks they are unlikely to be the only top predator. Most environments have something in the several hundred pound range. Large size helps conserve resources so some organisms will evolve towards it when possible.