1. If I understand the script correctly, it saves the collected data to a temporary CSV file. It then uses this CSV files to upload the data to a local SQL server database called CPUStats.
On the next iteration of the loop, that data is not imported as far as I can see.
2. The counter cpu.usage.average is good first indicator of the CPU load on the host.
For more details or in case you want to see what is causing a high CPU load, you will probably have to include other counters.
It all depends on what exactly you want to monitor/report with the script.