After returning to the forum I realized I hadn't answered all your questions. I am new at this site and have not heard of using Jobe Stakes in an aquarium. I do know that most fertilizers use urea as a nitrogen source. This is a highly water soluble form of ammonia and could cause all sorts of problems in aquariums. Urea is the chemical in urine that gives it its name. Look on your box of Miracle Grow to see its source of N (I used the last of my MG on my hostas and threw the box away). I am open to be educated on this, but I would not use anything not specifically formulated for aquarium use. I am looking at my box of Seachem Flourish Tabs and the only source of nitrogen I can find is protein hydrolysates. I am not sure how bacteria metabolizes this, or the end product, but it must be Seachem's way of providing N without the dangers of ammonia.
Kitty litter is not a nutrient rich substrate. It is a clay, (vermiculite), and provides the benefits of clay, hold nutrients until released by contact with a root. The word clay only refers to the mineral component of a soil which may, or may not, have nutrients. It may have some iron, and other micro-nutrients, but still needs a source for the macro-nutrients.
I have a layer of laterite under regular gravel. Laterite is another clay, rich in iron but not much else. The nutrients come from fish wastes and decomposing plant material (and the occasional dead fish which has swam, with its last bit of energy, into someplace I can't see). I am currently trying the Seachem Flourish.
Again, I hope this helps.
PS Using tabs or spikes in the gravel will certainly help your plants and I have used them, but may not provide the ideal environment for the lush growth people on this site desire.