To ask one’s father for one’s share of the inheritance early was unheard of in antiquity; in effect, one would thereby say, “Father, I wish you were already dead.” Such a statement would not go over well even today, and in a society stressing obedience to one’s father it would be a serious act of rebellion (Deut 21:18–21) for which the father could have beaten him or worse. That the father grants the request means that most of the hearers will not identify with the father in this parable; from the start, they would think of him as stupidly lax to pamper such an immoral son.
15:15. At this point, Jesus’ Jewish hearers are ready for the story to end (like a similar second-century Jewish story): the son gets what he deserves—he is reduced to the horrendous level of feeding the most unclean of animals. The son is cut off at this point from the Jewish community and any financial charity it would otherwise offer him.
On the indignity of running, it's noted that:
15:20. It was a breach of an elderly Jewish man’s dignity to run, though familial love could take priority over dignity after a long absence (cf. Tobit 11:9—mother and son). Given the normal garb, the father would have to pull up his skirt to run. Kissing was appropriate for family members or intimate friends.
The comparison to Tobit is interesting, but I'm not sure that the analogue holds--Anna being a woman and all was probably a little different than, say, a man.
15:25–28. Dancing was used in both religious and nonreligious celebrations. Elder brothers were to reconcile differences between fathers and younger brothers, but here the elder brother, returning at the end of a long day’s work, refuses even to enter the house. This is also a grievous insult to the father’s dignity and could have warranted a beating (cf. 15:12).
I'm not sure what the source for the notion that elder brothers were responsible for mediating such reconciliations is (none is given), but it does seem in keeping with the parable. All the preceding citations are from:
Craig S. Keener and InterVarsity Press, The IVP Bible Background Commentary : New Testament, ( Downers Grove, Ill.: InterVarsity Press, 1993)