Can you help me please about my problem with Blotchy lighting?
Have you thought of trying the Maxwell Render plugin for MicroStation? It's certainly slower than the default Luxology render engine but it gives far more predictable results.
I didn't do a good job of matching your original perspective angle but check out this comparison between the two render engines:
Glow light set to 20 instead of 1000 AA filter set to Gaussian and 64 samples per pixel....