1)
Bnei Yishmael dwell "me'Chavilah Ad Shur" (Bereishis 25:18)! Why were Amalek there?
1.
Radak: Perhaps Amalek dwelled there with Bnei Yishmael, or they took the land from them.
2)
Why does it say "Bo'acha Shur"?
1.
Radak: This is second person, addressing one who knows the place (when you come to Shur).