Why does it say "Ali Gil'ad"?
Radak: Even if you will ascend to Gil'ad to take sap (which heals), it will not help you.
Malbim: After Pharaoh's defeat [in Karkemish], he wanted to strengthen his reign in Surya, until Ever ha'Yarden, which was the capitol of this sovereignty. The Navi metaphorically calls this taking sap, which grows in Gil'ad.
Why does it say "la'Shav Hirbeis Refu'os"?
Radak: You take cures for your wound in vain. You have no cure! Refu'ah is a metaphor for your helpers, i.e. Kush, Put and Lud.
Malbim: You have no cure, because the core moisture and health ceased. I.e. you cannot be healed via other nations, since your choice Giborim fell.
Why is it written Hirbeisi, and we pronounce it Hirbeis?
Radak: The Kesiv teaches that they will say so when they fall. The pronunciation is the Navi discussing Besulas Bas Mitzrayim.
