Dallas grow bags coco coir hydro system - help

[TTRgreen2010]

Hello, I'm near Dallas (zone 8a) and would like a sounding board on my proposed hydro garden. This is my third year tinkering with a garden in the back yard and I think this one might finally be the one. Can anyone offer suggestions on my planned hydro system, please. Tell me why it won't work or tell me what I'm missing but please keep it as close to constructive criticism as you can (I bruise easy!)

The Layout
On the north corner of my lot there is an area that gets good sun till around 5-ish so this will be the site. I'd have a 35 gallon garbage can nearly buried in the clay soil as the reservoir which would be filled with nutrient solution. It's mostly buried to keep the nutrient temps cooler in the Dallas sun, except for about 10 inches or so to keep rain at bay. It would be sealed with its cover, hoses would exit as high up the side as possible and foam insulation would cover the exposed portion of the reservoir. A pump would push the water up a 1/2 inch pipe to a tee, where it is split to feed two nft channels. The reason I have two channels is 1) the area is square shape 2) some plants don't like to grow next to others so I'll separate them into the two channels a few feet apart and hope that's enough separation.

The nft channels would be made from 1x8's or 1x10's screwed together in a "U" shape, elevated by 4x4 posts and sloped towards the reservoir and lined with clear plastic to aid drainage. Inside the channels plants would be in grow bags. Then the channel will be covered with either a double layer of weed control fabric (which is black) or white/black plastic 6 mil draped over the top. There would be slits in the cover where the plants poke through only. The idea is that the water would flow through/down the nft channels where the coco coir should wick enough water to feed the plants and drain back into the reservoir. The cover is to stop algae growth and keep weed seeds and junk out. If I used the white 6mil it would keep roots cooler in the hot sun while reflecting sunlight back up to leaves.

Grow Bags and Medium
I have 10x 2-gallon bags and 10x 3-gallon bags on order (that, the pump, various bits for drip lines and timer are the only parts in my possession today). I'll fill those with 2/3 coco coir and 1/3 perlite or vermiculite for better water retention. In the tomatoes I'll add a cup of dolomite to give them the extra calcium they need (last year I crumbled egg shells in their containers).

What to grow
I'd like to plant tomato, bell pepper, zucchini, cucumber, eggplant, green beans, peas, carrots, green onion, garlic, and maybe a couple of others.

Companion Planting and Natural Pest Control
I am still learning about companion planting and I'll be trying it for the first time this year. Last year I planted broccolli with one of my tomatoes until I found out this will stunt the tomatoes growth. I also had that tomato planted next to a potato which increases chance of cross contaminating with blight.

Carrots will be planted with the tomato to take advantage of the "unused" air space at the base of the tomatoes. Most sources say carrots help tomatoes but I did find one dissenting source so it'll be an experiment. The onion and garlic is to deter ants - they loved my tomatoes last year but didn't seem to cause a big problem. French marigolds are said to repel harmful soil nematodes, aphids, some beetles, tomato hornworms, whitefly and even rabbits but bean plants do not like them. I may sprinkle some peppermint here and there because it's so good in tea but it loves to take over so it may stay in its own small containers.

In the same 3-gallon bag I'll pair a tomato with carrots, onions, basil and parsley. This bag will be next to a bell pepper with basil, parsley, and carrots.

I'll pair cucumber with dill (not near carrots), nasturtium and radishes. I may plant sunflowers in there as well so the cucumber will vine on the sunflower stalk/stem. Maybe. I'd have to keep the sunflower away from the green beans so it may be too much trouble. All this next to:
Zucchini with radish and nasturtium next to:
Beans which will pair with celery and spinach, next to:
Peas
Squash
Eggplant

On and on, you get the idea.

Secondary system, containers
Away from the nft (probably on the patio), in self-watering containers and "regular" containers I'll plant broccoli, spinach, lettuce. If I have any containers left (I only have 6 self-watering and 4 regular containers) I'll add bok choi/pak choi, brussel's sprouts, cabbage, cauliflower and maybe some spices like thyme and oregano, etc.

1. I'd like some suggestions on the companion planting aspect.
2. How far apart do the two channels have to be?
3. Because of the dolomite, is it ok to let the excess water from the tomatoes drain back to reservoir? Has anybody tried it?
4. Should I go ahead with the NFT idea or should I go with my gut and have individual drip lines for each grow bag? (I have 1/4 inch "soaker" hose to snake around the surface)
5. Is a 3-gallon bag big enough for a tomato? Bell Pepper? Zucchini?
6. The sun was so brutal last year, what shade cloth should I use and when should I put it up (don't want to stunt growth but last year tomatoes and peppers just shut down production till it cooled back down again)?
7. Heavy rains last year nearly killed everything, any thoughts on how to protect the plants (the black/white 6mil plastic may help???)
8. On the patio garden, which plants would need to be in self-watering containers and which can stand a bit more variability in their hydration?

Anyway, sorry for the long, long post. I just didn't know how to 'splain it succinctly. I'd appreciate any help or suggestions.