What is the significance of the number of men they killed?
Radak: They did not kill more, due to the merit of Avraham, who built a Mizbe'ach there "Beis Kel mi'Yam veha'Ai mi'Kedem" (Bereishis 12:8).
Why does it say "ki'Sheloshim v'Shishah Ish"?
Radak #1 (from Bava Basra 121b): The amount was 36. 1
Radak #2 (from Bava Basra 121b): They killed Ya'ir ben Menasheh, who was as important as the majority of the Sanhedrin (36). Me'iri (Sanhedrin 44a)
What is "Ad ha'Shevarim"?
Rashi (from Targum Yonasan): It is until they broke them.
Radak: The place is called ha'Shevarim because they were broken there (the enemy killed 36 of them).
What is ha'Morad"?
Radak: It is an incline descending from the city. That is where the enemy struck them when they were fleeing.
Why were Yisrael defeated?
R. Shilo (Sanhedrin 44a): Hashem said to set up the rocks immediately after crossing the Yarden, and they distanced 60 Mil before doing so. 2
Radak: It is like Hashem said (verse 11), because they transgressed the Cherem. 3
Radak: Why should we seek new reasons? Verse 11 gives the reason! Maharatz Chayos (44a)