“OK, cool” is a common way to tell someone you understand and agree. However, texting and the Internet being what they are, that phrase was deemed too long to type out. OK was abbreviated to k and cool became kewl which then morphed into k. KK?
Fam is your family but more often these days “fam” refers to any close loved ones, including friends. “I gotchu fam” is a popular phrase which means “I got your back.”
A cutesy way of saying someone looks good, hot or fine.