4. Further clarification
SAP ST02 cannot monitor SAP Extended Global Memory configured via EM/global_area_MB parameter directly. However SAP EG memory is part of SAP extended memory.
SAP ST02 memory monitor is one of SAP resource monitoring tools together with SAP operating system monitor (ST06) , SAP database monitor (DB02 or ST04) and SAP work process monitor (SM50/SM66). In my view, if there are free CPU power, free memory and enough free sap work processes, then a well-tuned SAP system should be healthy from SAP system performance point view. Based on SAP buffer and memory monitoring, the outcome of review can be one or several actions: increase SAP memory allocation at instance level, adjust memory quotas for individual process, tune application job/program and/or rescheduling job/program. How many memory can be configured is limited by physical memory and configured swap space for the server. Physical memory usage and swap space usage can be monitored via SAP transaction ST06.