I think the metal tree shot is a compromise between light and composition. You have wanted to silhouette it against the light but in so doing have had to take the shot from an angle that compresses its form rather too much for my liking. We can see the front on form of this sculpture through the nut of the first picture and a silhouette from that angle would look really great but you'd have to do something different with the lighting. If you are not averse to tinkering with PS, you could always have a plain blue sky behind the tree and then use the Omni light render to get the same effect as you have here.
The nut shot is well composed and it's just a shame that there are distracting fences and things on either side. The lines of the paving work really well as lead-in lines and perhaps more could have been made of these rather than have such a lot of space at the top of the shot. It's a shame that the tree sculpture had to be positioned with street lights around it making it hard to take an artistic composition such as you have tried for without getting them in. I think the clone tool is the only way around those here.
Well done on what you have done, you have looked for the best angles and compositions and you have done pretty well. The limitations are due to the fixed nature of the subjects and their locations, not your fault. They still work pretty well
Cheers,
Rob