so in the end the cell has 4 TCH TS, 1 PDCH TS, 1 BCCH TS and 1 SDCCH TS
when applying the Erlang B formula
4 channels @ 2% blocking = 1.05 erlang
so the values you are sharing are not abnormal. It is rather high though, one should expect about 2% congestion, not 6-10%. Did you properly activate the TCH Queuing ? Is T11 around 6 seconds ?
Also, try to decrease the max pdch to 4 instead of 5, and reduce the HIGH LOAD GPRS by 10%