Food web question

[ReMuSoMeGa]

I don't fully understand the concept of grazing food webs & detrital webs
In specific, how can energy/matter be transfered from a detrital web to a grazing food web.

-My book says that an earthworm eating dead leaves is an example of this.
-A bacterium decomposing the feces of the worm is not.

Any dead organic matter or waste is part of the detrital web, correct?
When a bacteria or fungus decomposes this material, where does the energy flow to? Isnt it converted to NH4+ via ammonification, then back to the plants to join the grazing food web?

Is any organism that is prone to be eaten alive part of the grazing foodweb? What if we are considering a highly poisonous type of insect that will kill whatever eats it. Would this insect still be part of the grazing web?

Finally, my book uses the words detrivores and decomposers interchangeably, but makes no distinction. Is there a key difference in these words?

Thanks for reading

[ReMuSoMeGa]

anyone?