Abraham's Wives, Abimelech and Phicol

A couple different (smaller) things confused me about today's reading so I'm sharing what I found:

1. In Ge 25:6 it says Abraham "gave gifts to the sons of his concubines." The Concordia Self-Study Bible notes on this "Polygamy was practiced by even godly men in ancient times, though it was not the original divine intention," which seems to assume that besides Sarah, Hagar, and Keturah, Abraham had concubines as well. However, other commentaries mention that "concubines" probably refers to Hagar and Keturah. Kretzmann's Popular Commentary says "Although neither Keturah nor even Hagar were concubines in the later sense of the term, yet, in comparison with Sarah, the mistress and mother by special divine interposition, they were of secondary rank."

2. In the account of Isaac in Gerar where he, like his father, says of his wife "She is my sister," you have the mention of Abimelech and Phicol. I was curious: "This many years later are these the same guys?" The Concordia Bible says their names are "either a family name or an official title, since [they] reappear over 60 years later in a similar context."