Welcome to the community. To answer your question 2:
The timestamp is in EPOCH format, there is plenty of information on the internet with provide detailed information. An online converter can be found here https://www.epochconverter.com/
Standard Epoch times are measured in seconds and have normally 10 digits size for current dates.
The “created_at” returned on my example is 17 digits long. Is there some extra information I am missing?