Fine tuned some parameters and fixed the random angle sample issue. nMin=64, nMax =128, render time 4minutes 26 seconds
Render time 28 sec with nMin=4 and nMax =32
Sample Count image with linearly interpolated sigma threshold between 0.0005 and 0.0001
Render time 1:21 with nMin=16 and nMax =64
It's strange that so few pixels would need the max number of samples when there are so many places where pixel value overlap could happen
Specs
Processor: Inter(R) Core i7-35337 CPU @ 2.00Ghz
RAM 8.00GB
NVIDIA GeForce GT 740M