Hi Alexander,
nice chart! 
You don’t need to do full zoom-rounds but I would place them at more sides, 3-4 at least.
Also, consider different height levels - the more angles, the better.
The number of shots in each cirlce depends on how dense your object is - the denser, the more images per circle.
The light will be no problem whatsoever - RC is really good about dark areas, so as long you can see something and there is no bad noise, you should be fine. The only problem could be the texture, but even that is handled well usually. And since you don’t care about it, even better!
Since you say you want to get the best possible result, I would rather suggest a fixed lens and also strongly recommend to use tiff instead of jpeg. Jpeg is good for many needs, but it can make a small difference. If you have drivers installed so your raws can be displayed by windows, RC can use them directly.
The level of detail is only limited by the resolution of the images. In my experience the smallest detail should have at least two dozens of pixels across the width to get anything, more if the texture is tricky. That’s just a rough guideline of course. But you can’t expect anything if your thinnest twigs are only a few pixels wide…
And really make sure that there is absolutely no movement of the branches whatsoever - though from what you described of the size that seems almost impossible to me. Hanging it like ShadowTail suggested is a clever idea, but how will you prevent it from turning slightly?
About the green screen: If it is such a big room, you might be able to set the DOF so that the background is so blurry that you don’t need the screen.
What you mean by coded targets are called Ground Control Points in RC. It does work really well although not automatically recognized. It will only work if the targets stay in exactly the same position in relation to the object, so it won’t work with the haning scenario.