Nice that you read Graham’s book, and a lot about decreasing minerals in food. They are hard to measure though, and I am uncertain of the difference made by rickdusts, though I use them sometimes, and actually prefer lava dust – but it is hard to buy in Britain.
Quite alarming about farming and the reason you cannot find organic rapeseed oil is that it is barely possible to grow organically, because of the difficulty of weed control. I think it is only since the invention of weedkillers that rape has become such a widely grown crop. In an organic world, I am not sure what our plant based oil might be in the UK and there is a case for eating butter! (organic milk is realtively easier)