Think I found a cure for dead and sandy soil

I live on the Coast in BC, Canada. Although we have a very temperate climate and relatively long growing season, the soil out here is mainly sand with a small amount of "forest floor" material - decayed ferns and cedar and other conifer material.
I have recently been trying out some agricultural fertilizers with amazing results.
The primary thing that seems to be missing from a sandy/gravelly mix is "humates" or decomposed organic material. (Hey I am a novice - learning this stuff as I go - so correct me if I get stuff wrong!)
I brought in a ton (20 x 100 pound sacks!) of compost from the local garden center to augment soil in the spring, but we have quite a large garden so even that much compost was just barely enough to work a gallon or less in around each of the plants. Plus, the compost from the garden center, although very cheap, is nowhere near as "active" as my own compost so it had only a modest impact.
Then I found out about Humic Acid.
Humic Acid is a liquid solution the main ingredient of which is basically prehistoric compost. Because it is so extremely decomposed, it is accessible on a micro level for direct assimilation by the plants. That's what they say, anyway.
However, because it is essentially "humates" it sticks around in the soil - unlike chemical fertilizers - and appears to actually be building up my sandy soil! The main difference I notice - other than the incredible condition of my plants - is that the water does not just run through the soil as it does with sand. Now that I have been using Humic Acid for a few months, the soil around the watered plants stays wet for much longer as the humates in the soil help retain the water.
Apparently Humic Acid is used in hydroponics to help make micronutrients more accessible to plants in the nutrient solution they use, but I don't really know much about that - not into hydroponics myself and am really only a novice gardener.
I only really got into all of this because the place we moved into in January has a big garden and I very quickly tried to figure out how to hang onto as much of it as we can since the soil is so sandy and in the rainy season the erosion is extreme.
Here is a link to the place where I have got my Humic Acid - they were recommended because their Humic Acid is a 15% concentrate which is apparently the strongest one you can get.
Anyway, I hope this is helpful for anyone else who is struggling with sandy soil and dead soil and severe erosion.
Has anyone else had experience with Humic Acid? Or are there other soil builders like this that work well?
The Humic Acid seems expensive (I think my gallon jug was about $80. Canadian - about $60 US), but I only use about 20 mls per 12 gallons of water so it goes really far. I have only used about 2 quarts in about 3 months on a fairly elaborate garden that spans well over 2000 square feet - a lot of it rock garden.
Any feedback on this stuff? Anybody tried any other stuff from these guys?
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