1.How the load is distributed across processor cores (12 cores/2 cluster)?

The cores are distributed between different tasks dpi by functionality that they do not interfere with each other
2 and 7 cores are responsible for traffic transit and not very loaded. 
To see the distribution of functions can be command:
ps -p `pidof fastdpi` H -o %cpu,lwp,psr,comm

2.Why DPI have not loaded the CPU core (12e not used core)?

In dpi there are service functions: netflow export, clickstream, pcap export,
processing of control commands, and so on. Their load is uneven and they can temporarily 
load the core for 100%, so they are allocated on a separate core that they do not interfere
with other funtionality for instance - transit

Administration issues