The Fremen in Dune are clearly inspired by Muslims but not necessarily Arabs. They are more closely modeled on Chechens. Fremen words like "sietch" and "kindjal" are from the Caucasus.
Not sure about that, there is a lot of overlap with bedouins. The harsh desert planet in which they have learned to thrive is now highly desired by outsiders because of the spice (oil).
The book "The Sabres of Paradise: Conquest and Vengeance in the Caucasus" is usually given as one of the books that influenced Frank Herbert.