for a cell with 8 TRXs you should define 3 TSL as SDCCH(8) if you are using Full-Rate or 5 TSL as SDCCH(8) if it is Half-Rate. But keep in mind that this is only initialy defined values. After some measurements you may need to increase the number of the SDCCH channels. I have no idea about the traffic model of the network where this cell is located.
Generally you are right, the bcch frequency band is not mandatory located on the lowest frequencies, it depends on the planning strategy.