[GpsFrontier]

If I sink the reservoir into the ground it sounds like it would be more of a challenge to flush it, clean it out, etc? Is it worth it to sink it into the ground, or maybe find a solid white 55 gallon drum or something smaller?

Yes it can very well be more of a challenge to clean out in the ground. With the reservoir above ground the reservoir will basically the same temp as the ambient air temp, unless other things cause it to rise or cool. Like sitting in the sun, or on a cement slab that absorbs heat all day etc.. The optimum nutrient temperature is between 68 and 72 degrees, but depending on many variables plants can survive higher water temperatures. Generally speaking water temps above 80 degrees, and the plants will be stressed. Much above 82 degrees and the plants may begin to abort fruiting in order to stay alive. Temps below 60 degrees and the plants begin to grow much, much slower.

Inside a climate controlled greenhouse the nutrient temp would likely be about the same as the air temp inside the greenhouse. Though the more water volume there is, the slower it will raise or lower. So when the night time temps lower the water temp, the more water there is, the slower it will heat up during the day. But the longer it takes to cool at night as well. I have built a easy to clean in ground nutrient reservoir, and although it was a 20 gallon reservoir, the design is quite simple and easy to make bigger if you find the right containers. I will e-mail you my design plans, I created the pdf for my website. But for now here is a link to the post of the easy to clean in ground 20 gallon reservoir I built for my tomato plants.

How often do drips really run to be as efficient as possible, and at what rate? Does it run at night?

I have never ran a non-recirculating system (run to waist). But every growers situation/environment/growing conditions, as well as all the other many venerable are different, so watering schedule's are something every grower really needs to work out for their situation and plants. Basically you just need it to run long enough to keep the roots moist (not saturated), and not off so long they dry out in-between watering. Regardless of type of system, and/or recirculating or not. Also plants don't really take up water/nutrients during dark, so I cut back on the watering schedule during that time, but I still don't let the roots become dry.

Should I just make the link drip into the middle or use a hoop style drip line?

As long as the growing medium/root ball is moist it dosen't really mater. Just don't let the stem of the plant get to wet, then they may develop stem rot. Typically with non-recirculating systems (run to waist), they use dippers to control excess water usage. I personally stay away from those dippers because they easily clog. I like to make a drip ring and just poke holes in it with a hot paperclip. Much cheaper than buying dippers that will wind up clogging. However I have never used a drip system with 3 inch net pots. If you decide to make drip rings make sure they don't kink when you bend them into a circle. I have also herd that soaker hose works well, and dosen't clog when used as a drip ring, or even as an air diffuser when used with an air pump instead of air stones (that's on my list of things to try myself).

P. S.
I'm not sure there will be enough room to grow the plants you plan. The layout is very tightly spaced together, and most of the plants on your list like tomatoes, squash, zucchini, beans, cucumber, and eggplant are all very large plants. You may have already worked it out, but from the greenhouse layout and how tightly everything is packed, I don't know how you will be able to pull individual tubes out for for maintenance. Or even get to most of the plants for trimming, tying up plants (trellising), or harvesting etc.. Also I saw the bee hive in the videos, is that how you plan to pollinate the plants in the greenhouse?