The temperature setting for your boiler depends on a number of factors. As you will read in the linked articles, some boilers maintain no minimum temperature. They simply start up when there is a demand for heat. Other boilers are installed with zone thermostats that control circulating pumps. The boiler temperature is maintained at a constant, and the thermostats simply control the pumps which moved the heated water to the desired location(s). My own boiler has a minimum temperature setting, simply because of the size of the boiler and the lag time involved in bringing the boiler up to temperature.
This minimum temperature is a function of the size of your boiler, the size of your house, and the heat loss from your house. The optimum setting can only be arrived at by experimentation. My personal experience is that the minimum boiler temperature should vary through the heating season. If I set my boiler temperature to where it should be in January and February (140F), my house overheats in November and March. In years when I'm lazy, I just leave it at 120F.
From the information that you have provided, you also have a very large boiler, and may find yourself in circumstances similar to my own.
The high temperature setting, and the pressure setting, have nothing to do with operating the boiler. These are safety controls to shut off the boiler if the temperature or the pressure get too high. They are typically set at 210F, and 30 psi.