Good to hear you have things leveled out. I have been out all day running errands, and didn't get home till about 9pm. So I haven't had time to come up with much for you yet.
Since you have everything glued together, it's basically imposable to make changes. I can't really tell from the pictures the angles where your tubes are bowing. But I think a lot of it may be due to the construction methods. Especially if they are bowing sideways, rather than downward. For a design like that, all the pieces would need to be cut exactly to the same size. and everything be measured and precisely installed. So all the spacing is exactly the same with any tube that it runs parallel with. If not, it will cause that kind of bowing. It would give the same effect as the tubes being all cute to different sizes, then the ones that were longer would begin to bow as they are compressed to fit in the same space as the shorter ones. An 1/8 inch off on one side can result in more than a inch or more off on the other side. Then forcing them together will bow the tubing to make it fit.
But now that it's all glued together the easiest and cheapest thing I can think of is to to to try and straighten them with 2x4's. fintuckeyfarms did something very similar to her first system. She ran a straight 2x4 underneath it and attached the tube to it. You can see it in the pictures she posted in this thread. You can use anything from zip ties to duct tape to strap the tubes to the 2x4's.
Fintuckeyfarms bowing was due to supporting only the ends of the tubes, rather than spacing it for the weight in the center of the tubes. So her bowing was downward. Sideways bowing needs side supports/splints. I made some drawings to show you what I was thinking. It probably won't look the prettiest, but it should be much cheaper than starting over.
With an NFT system the way you designed it, it will be very important to have all 4 tubes angled exactly the same. Unless you plan to have a separate water line for each of the tubes with plants, the water wont drain to all 4 evenly otherwise. Even if it is perfectly level, and you only have one water line to flow water through all 4 tubes. The tubes closest to the water line will get most of the water, simply because water will go downhill the first chance it gets.
You may consider a irrigation manifold like this one
Orbit 4-Port NPT Irrigation Manifold with Filter, to split the one water line into 4 lines. You will need a couple extra adapters to get the vinyl tubing from the
pump to connect to the threaded manifold, but their not expensive. That size line (1/4 inch) coming off of the manifold to the system should be fine for a NFT. You are just looking for a thin layer of water flowing by at the bottom of the tubes in a NFT system.
However you will need to adjust the water level higher in the tubes until the roots are long enough to reach the thin layer at the bottom of the tubes. I'm not sure if you have that worked out or not, and it would be nice to see some updated pictures first in case you made changes that would affect my ideas. I see your downspout is facing down, I can think of a simple adjustable overflow with the way you have that set up. But I will need to make a drawing to explain it clearly though. I don't have time to do so right now (it's 1 am), but I can do it tomorrow, and have it posted by late tomorrow evening if your still interested. I'm not sure what you have worked out so far.
PS.
I hate to say this, but another drawback to having everything glued together the way you do is that it will be imposable to get the root systems out, not to mention to clean and sanitize the inside for your next grow. You always want to think about how you will be able to do maintenance when building your systems. You want to be able to maintain your plants while they are growing. You don't want to need to kill your plants in order to fix an issue that may come up. It costs money to build them, so you'll want to use them over and over. So it's very important to think about maintenance. You saw the thread on the peas I grew, I attached a picture of the root mass that was inside. That picture doesn't even include the roots I cut out with a knife to get the baskets out.