The term "Soil Food Web" is used to imply a very complex system which involves much more than the individual workings of each organism. The whole is far greater than the sum of the parts.
Soil biologists I've spoken with almost always point out that they might understand less than 1/10th of 1% of what is happening between soil organisms and how the effect plant health.
There has been a great deal of study done on the Soil Food Web both in the scientific world and with field work. Much more needs to be done.
I don't know if you will get specific answers to your questions on lawnsite. They are good questions, keep asking them but also do your own research. Look up "Trichoderma and disease control" for a start.
The nation that destroys its soil destroys itself.
Franklin D. Roosevelt