Regarding question Why I'm not using 100%?, it seems that maybe IBM's JVM (shipped with WAS 8.5) is still using green threads, am I right?
I can't image why it would be using green threads nor does the chart you showed suggest it it.
You have a machine with 32 logical process which are about 50% busy. This means about 16 native threads being used.
A more likely cause is that the process is locked to one of two sockets and this would explain the about 50% usage.