Regarding the freezes: For what would I have to look in the logfile?
This *_processors settings seem to be some kind of voodoo black magic 
E.g. I found this here, where they use
processbuffer_processors = 72
outputbuffer_processors = 128
for a 16 core machine.
“Increasing the output batch size did negatively impact the performance so we reduced the batch size to 100, which is 1/10th of the default value. At the same time we increased the processbuffer_processors and outputbuffer_processors quite a lot. So the current settings, that seem to be a sweet spot are really the opposite to the best practices.”