parable of the shrewd manager

Luke 16:1-15

This is one of the most difficult parables in Luke and one that I've wrestled with. What exactly does it mean?

In this parable, Jesus says that a steward was given the pink slip by his master because he was wasting the master's possessions. The steward, not having any other marketable skills, cuts the bills of his master's debtors by 50 and 20 percent, so that they will think highly of him and help him when he is fired. The master praises the "dishonest" steward for his shrewdness.

There are three views on what the steward did. At face value, the first view always seemed like what happened, but Jesus' application never made sense to me because of it.
1) Traditional – the steward undercut the master (thus, the master calls him dishonest, but also "shrewd"—in this case, using worldly wisdom)
2) The steward removed the interest charge
3) The steward removed his own commission

Any of these three would have made both the steward and the master look good, and so the shrewdness of the steward is seen.

The pros of #3 include:
a) The master would have commended him #3, but I have a hard time seeing why he would commend him for cheating him (#1)
b) The wisdom of #3 lines up more closely with the Greek word for "shrewd" (wise or prudent) than does the worldly wisdom of #1
c) #3 makes "dishonest" in v.8 refer to v.1 (wasting the master's possessions), not to what the steward did in v.5-7
d) From the IVP Commentary: "The steward has sacrificed what he could have taken now and has given it to others so that he can receive gain later." The steward sacrifices nothing in #1-2.

I believe letter d jives the most with the point Jesus is making: be generous and wise with your money (included here is sacrificial generosity). Think through what you do with it. Help people. Here on earth, you will make friends for yourself. But this is also an eternal perspective. This is loving God, not money. If you can be trusted with little, you will be trusted with much, but if you can't be trusted with this world's wealth, you won't be trusted with true riches—kingdom service—serving God and others. This also shows the high honor of serving God.

This passage finally makes sense to me! Now I just want to know what v.18 is doing in this context.