You may be ready to segue into organic gardening, which emphasizes soil building and integrated garden systems (e.g.,beneficial insects, compost, companion planting) rather than conventional gardening, which tends to look at soil as if it were an inert substance needing to be fed specific fertilizers based on what we feel is needed.
But organic gardening isn't a "Do this instead of that" practice; it's an entirely different way of approaching the garden.
Take a look through the Organic Gardening Forum to get an idea of the (many) options available.
An introductory book on organic gardening, perhaps from your local library, may give you a more coherent base of knowledge.
Yes, you're right: synthetic fertilizers *can* do more harm than good, including burning roots, leaves, etc.
USDA Zone 9, Sunset Zone 17