Good read. I like the way you monitor your nutrient uptake.
I grew lettuce over the summer using a kratky rig that looks identical to yours minus the pumps and air stones. It worked great for lettuce but I don't think the kratky method would work for the devil's cabbage .
First of all i think this is the easiest way of hydroponics but i have a guestion.
Could this be done if i just use netpots with hydroton and fill the resevoir with lets say 3-4 cm? Ofcourse use a pump to circulate the water