I've been working with red wigglers for a couple of years and still have a lot to learn. That said, I have a system that works which I will describe below. It probably won't
answer all of your questions, but I am not really convinced that the questions you are asking are appropriate for the amount of castings your worms are likely to create - at least not unless you intend to create a really large-scale worm farm. Initially, I would focus on process and, once you have perfected that, refine your quality.
Goals: my own goal was to improve the speed of my composting without back-breaking work. I don't have enough kitchen waste to effectively hot-compost more than once a year - when I have lots of fall leaves to add to the bin. Worm composting is a great alternative for part of my kitchen waste. It would be difficult, however, for me to imagine managing a home-based worm composting system that could provide an entire garden with sufficient compost to significantly build up the soil. If you are trying to amend a large amount of space, worm composting is probably not the solution. Otherwise, I second the other folks who say that knowing your goals, and whether or not they are achievable with your worm bins, is very important.
Quality: at first, don't worry too much about the quality (apart from the acidity) of materials going in or coming out until you have perfected the mechanics of your own system. The quality of my own castings is not laboratory tested but works great for me. You can always amend your soil with additional nutrients after the worms have done their thing. If you are particularly concerned about the resulting quality, have it tested by a soil lab and tweak it. But you'll have enough of a
project in your first year just getting the system balanced and perfected.
Quantity: if you want to create a lot of worm castings you are going to need LOTS of breathable, horizontal bin space, and lots of input. For every 5 gallons of vegetable scraps, you may get one gallon of worm castings. And it's going to take some time and attention. My own system requires 5 bins going simultaneously in order to simply consume all of the veggie scraps from our 3-person household. Out of that, I might get a gallon of castings per month. Much could be done to improve the design and
footprint of my system, but I have not reached the point where I am needing to optimize for space.
Design: for my worm bins, I use a stacked, three 5-gallon
bucket system. The top two buckets have holes every inch or so in the top and bottom, as well as a double line of holes (again 1 inch apart) just under the lip of each bucket. The holes in the bottom of the top two buckets are large enough to let the worms pass up and down between buckets - about 1/8" if I remember correctly. The holes in the top, and around the rim, are a bit smaller. As discussed, this takes up more space than it should, since the resulting "towers" are as tall as three stacked, food-grade, 5-gallon pails. But the layer of worm castings can really be no deeper than a couple of inches -- otherwise it starts to go anaerobic. In other words, each bin system could probably be reduced to 10" in height if I had the motivation to do so.
Moisture: one thing that took awhile to perfect was the proper moisture level. Too much dampness leads to stinky bins. Everyone loves to talk about "worm tea" (ie: the leachate that collects in the bottom bin of the system) but I have found that a noticeable accumulation of worm tea is usually a sign that my bins are too damp. Perhaps, if the bins are operating at optimal temperatures, and if you are removing the leachate through a well designed drainage tube, you might be able to accumulate this while keeping your system healthy. I have not been able to manage that balance, so I don't let the bins get so moist that they collect much tea.
To manage moisture, I shred junk mail and scrap
cardboard, avoiding colored inks and glossy paper. I keep a bag of this near the bins and toss in a handful with every quart of food scrap. Because I do this indoors, using shredded leaves is not convenient. The paper, however, works just great to take up extra moisture and help with aeration. It also breaks down well during the process.
Input: to determine my input, I try to think like a worm. If it seems like it would be unpleasant to crawl through, I don't add it. I don't add citrus peels, onions, ginger bits, egg shells, etc. Instead, these get mixed with the leaf compost, the egg shells helping to balance the acidity of the citrus. If I had animal waste, I would definitely add it to my worm bins, but I do not. I am not sure how well that would work in an indoor system like my own.
Time: I spend a little time with the worms every day or two. I find that it helps to turn the castings a couple of times per week for aeration and to make sure everything is going right. Since two of the buckets in ever tower often have scraps and worms, it is good to assess where they are in the process and whether it is time to stop adding scraps to the top so that the worms make their way into the bottom bin. As the castings get closer to done, I'll manually relocate worms to the bin below for a week or two before removing the resulting castings.
Finally, I don't know if anyone has mentioned this yet but you don't want to let your castings dry out entirely, or sit in the sun, before using them. The worms create a living soil that require moisture to maintain its vitality. If you dry it too much, or expose it to UV rays, you are probably killing valuable microbes.
Again, I still have a lot to learn about the actual science of the process. What I do know is that this system seems to encourage a healthy population of worms, zero problems with fruit flies or other pests, and about as much worm castings as can be expected from any system. It reduces my household waste stream considerably, and fits in the space that I have. My naive working theory is that, if the worms appear happy and healthy, it's good enough for my purposes.
Set reasonable goals for yourself, and realize the likely output of your system. If you focus too much on the minute details in the beginning, you will probably get overwhelmed. Let the worms do their job and, once you are comfortable with your system, consider scaling up to meet your hopes and dreams.
Cheers,
Karl