carbon, hydrogen, oxygen, this is what "hydrocarbon" means, i believe you can easily find out their individual proportions in the earth's crust (these are estimates of course)

it's not a high proportion... alumnium, silicon, iron, magnesium for sure are more prevalent than CHO, most soils are primarily silico-aluminates and we know by the field that much of the core is iron

it is way overstated how much water is on this planet, it's just a thin layer on the outside, and that is 2/3 of CHO

also just to point out it's been recently published that sources of hydrogen in rocks are more abundant than previously known, not hard to see how water eventually formed if you add volcanic heat and silica and hydrogen, more or less just a numbers game