Answering these questions in order but I can definitely go into more detail in person, so it doesn't feel so dry.
- It was the timeline that, in short, had to be kept on course in order to prevent another Time War. - Creator of the TVA. He was a crazed supergenius who went forward enough in time to know that if specific variants of himself came into power, war would break out and he used the newfound knowledge to prevent that from happening. In a way that wasn't exactly correct. - If they're from our universe, a fair amount.