Will foundation wall be strong enough surrounded by gravel?
In silt soil, for drainage I plan to put clean gravel next to the cement foundation walls which will go 4 feet into the ground in a trench and extend 2 feet above the ground, with the house floor above that; so the gravel would go the length of the wall, with a drain pipe at the bottom next to the bottom footing in the gravel on exterior side.
Would that be stable enough for the wall though, or does it need to be more compact? I was going to also replace about top 6 inches to a foot of the dirt on the floor of the ground-level crawl space with gravel as well, and that would be vented in there on all sides. I am thinking a vapour impermeable membrane over the floor would not allow moisture to escape, evaporate or drain. I was only planning asphaltic dampproofing on the foundation walls. Does this sound like a good plan?
I'm not sure what you mean by stable enough, presuably you have a poured concrete wall that is structurally solid and able to to withstand the pressure of exterior fill? I don't understand the question about supporting fill and compacting it, elaborate a bit if you like, however that may be more a question directed at whoever designed and stamped the foundation plan?
As for your crawlspace - a vapour-impermeable membrane is the smartest thing you can do. without covering it, a stone or dirt floor in crawl spaces will endlessly and continously supply moisture into the space. Read more here -
How to insulate and waterproof a crawl space to avoid and prevent future mold
The damp proofing tar that gets sprayed on foundation walls is far better than nothing and should be alright, better still is a dimple foundation membrane, though if its not living space down there and you manage moisture then that may take your project over the budget you intended.