Parshat Vayera: Something old, something new

Here's something old concerning Yishmael/Ishmael, and also something old about the Akeida/Binding of Isaac.

Here are some new thoughts that I had yesterday:

The commandment of brit milah/ritual circumcision and the announcement that Sarah would have a son were given at the same time, and the text says very clearly that Yishmael was circumcised when he was thirteen years old. (See Parshat Lech L'Cha, Genesis chapter 17.)

Now here we are, in Parshat Vayera, with Yitzchak/Isaac conceived, born, and weaned, and yet the text of Genesis chapter 21, verses 14-16, describes Yishmael as a "yeled," a boy. Here's a translator's nightmare: "va-tashlech et ha-yeled." Did Hagar cast the boy under a tree, or did she send the boy under a tree? Unless my Hebrew is completely off, either translation would be correct. The translator chooses "cast." Why? Aside from the obvious problem that parents don't generally throw their children, the kid must have been around 15 years old! The original Hebrew alternates between calling Yishmael a yeled (boy), and a naar (youth). Were two different texts cobbled together here, with the seams showing, as usual?

And why does Sarah disappear from the text? Where is her reward for having ensured the perpetuation of Avraham's lineage by offering her handmaid as a surrogate mother? Where is her reward for having waited over a decade after the birth of her handmaid's son to have a son of her own? Where is her reward for having saved Avraham's life twice--and enriched him in the process--by allowing herself to be passed off as only his sister and not his wife? Her reward is to have G-d, with her husband's cooperation, threaten the life of her only child? My own midrash: No wonder she dies in the next parshah--if this is her reward, why live?