My suggestion is that you go to the Performance section of the ODM and decide which option you want. Don't have the book here with me, but I seem to remember that the options were Min Block time, Min Cost or Min Fuel.
In terms of the "limiting Tq", we use Tq figures from the ODM, presented as a "Climb Chart" to the crew. You simply check Altitude against temperature at that level and apply the Tq figure shown on the chart - the check is done every 2000'. Makes life easier for the crew and standardises the Tq setting. The same type of chart is used to set the cruise power and determine MCP.
The chart used is a simple box chart with Altitude on one axis and temperature on the other. Enter at altitude, read across to Temperature and you get the Tq setting.
Here's another tip for your SOPs. The 300 is quite capable of reduced power takeoff. It really saves the engines and lowers the costs. Use 90% for the first flight to ensure the power is available, then reduced power for the other takeoffs.
Hope this helps.