That is based on a particular reading of the translated text. The Hebrew words for “thousand”, “group”, and “chieftan” are written the same (LP) (the last one has different vowels from the earlier two).
If we take the thousands values as numbers of family groups, and the number after that as individual males between 20 and 60, then we get about 600 family groups and 5,500 adult males, and given population demographics of the day, about 20,000 individuals. This also gives a plausible population growth rate of 2.85 surviving children per couple (for 25-year generations).
No, it was a people group Israel cited by Merenptah in records of an Egyptian raid in the area.
We can tell that there were many significant building projects in the area c. 1050-950 BC. We can also tell that the area was fairly wealthy, in contrast to the previous few centuries. We have very few records from the area (other than the Bible) about anything prior to 950 BC, so the lack of them is merely uninformative.
And, as I said