1)
What is the meaning of "va'Yanchem"?
1.
Radak: This is like "Nachisa v'Chasdecha" (Shemos 15:13) - he led them and brought them in front of him.
2.
Radak citing Targum Yonasan: He caused them to dwell.
2)
Where was the fortress?
1.
Rashi: It was near Mo'av.
3)
What happened after David left the fortress?
1.
Rashi (from Tanchuma Yashan Vayera 25): Melech Mo'av killed David's parents and brothers, except for one, whom Nachash ha'Amoni kept alive. This was David's intent when he said "Ka'asher Asah Aviv Imadi Chesed" (2:10:2).
