50 meters high is about right and is about the only solid(?) information you will find, the rest is all pure speculation.
And for reference pictures, that depends on what you are actually looking for.
First of all keep in mind that it's all pure (final) fantasy. Scaling is a real issue throughout the whole world here, scenes don't match up and to be honest the story about Midgar is bigger then Midgar itself.
For references you could base your Midgar upon:
- The original FFVII
- The Midgar from Crisis Core
- The physical Midgar model from SE-hq
Those are three completely different versions.
Personally I've based my version upon FFVII the game.
an early version of this:
To have a bit of a feeling about scale on the plates this is a (again early) view of the most important parts:
and zooming into sector 8 for a sec:
Coming back to thhe scene you're working on with the elevator, I would do it seperately, unless your able to animate the reflections of the elevator itself as well. Looking at how the scene (in FFVII) is build up the layers are clearly seperating the elevator from the background. You would be better of to create the backdrop in 2d rather then building the whole of Midgar for this scene alone.
As for what's wrong with the model, I think the borders are to thick compared to the size of the plate. Also the central train pillar feels of, to thin.
The following is (supposed to be) more or less 50 meters high;
And if you look into the technical bits and bobs of locomotives, it is a real miracle that it will ever get on top.
But look close at what is available, the background of the dropping above midgar is a source for getting a feel for the width of the pizza, if you set the pilar(s) to 50meter height, you can scale the rest into proportion.
I wonder what your goal is here, is it just to be able to create the scenes in the Q-gears engine? or do you plan on actually rendering the backgrounds for the qhimmed-FFVII? (just wondering).