Chapter 20 opens with another very strange parable, as the SAB puts it, "The parable of the unfair, lying employer." Rather than try to describe it, I'll let you read it yourself. A note on the face of the parable's content that I think is needed is that "a penny" is not a direct translation (it was actually a denarius, a coin worth ten times another smaller Roman coin, and commonly paid for a days wages), and the agreed wage was reasonable, or else the first group certainly wouldn't have signed on. The latter groups of workers are told "whatsoever is right, that shall ye receive." Now in the matter of unfairness, I can certainly see where the argument comes from: if you've got groups of people working 12, 9, 6, 3, and 1 hours, and you pay them all the same, it does seem unfair, I'll grant. But lying? Look, the first group agreed to work for a penny, so there's no lying there. If all the other groups agreed to work for "whatever is right" then that's subject to opinion, namely the opinion of the owner of the vineyard. The accusation of lying seems like quite a stretch to me.
So what about the unfairness, and the meaning of the parable? As I've said before, I can only guess, but it's always seemed to me that this parable is talking about the gift of salvation, and how even if you spent your whole life going to church and being a good person, spreading the Gospel, you get just as much salvation as someone with a deathbed confession of faith who goofed off their whole life. The SAB asks what the meaning of verse 15 is, and I think I know this one; "Is thine eye evil because I am good?" is, I believe, supposed to mean "Are you giving me such a dirty look just because I've decided to be generous?"
Did Jesus forewarn the apostles of his death and resurrection? Yes he did, but the fact that they failed to understand, as John 20:9 points out, is a separate matter.
When we are told the story of the mother of James and John asking for seats of honor for her sons in the coming kingdom, the SAB points out that the parallel passage in Mark doesn't mention the mother. I figure that this could be a matter of Mark not noticing (or not mentioning) the mother being there, and in the real story, it wasn't her personally who asked, but rather that she goaded her sons into asking. The SAB may not agree, but that makes both versions work out fine in my estimation.
How much power did Jesus have? This is a good question, and I think I addressed part of this previously, but there's a special case here in this chapter. As I think I mentioned before, the passage in Mark 6 isn't about Jesus having a lack of power, but having a lack of opportunity to show it. In Matthew 20:23, the issue is not so much that Jesus can't choose, but that he's allowing that choice to be given over to the authority of God the Father.
The SAB asks "Was Jesus a ransom for many or a ransom for all?" to which I'm going to respond that this is just splitting hairs. If Jesus is a ransom for all, doesn't it logically follow that he was a ransom for many? Maybe I'm missing something here. The SAB further asks "Who (or what) is the ransom for the righteous?" and pulls up some confusing verses. Honestly, the really confusing verses are the ones from the book of Proverbs, and the Hebrew term used there seems to really mean "ransom" (it has other meanings, but none of them seem like they would apply) so I'm not sure what is really meant there. One possible interpretation, although I think it might be a stretch, is the thought that on the cross, Jesus was transformed into our wickedness in order that we would be deemed righteous in his stead, thus making Proverbs 21:18 into a sort of explanation of Jesus's substitutionary sacrifice. I've really no idea at all what to make of Proverbs 13:8.
Finishing out the chapter, we have the story of two blind men sitting by the road near Jericho that Jesus healed. The SAB points out some discrepancies between some similar stories in the other Gospels and claims them to be contradictions. Maybe they are, but the way they could be contradictions is manifold. Perhaps there were two blind men, but Mark and Luke only remembered one. Perhaps there was one blind man coming in, and another going out. Why is it that Mark knows the name of the blind man, but he/they were anonymous in the other stories? In the end, I don't know what's going on here. Perhaps one or more of the authors got their stories wrong. Perhaps this isn't different tellings of the same story, but is two or three different incidents that happened in about the same place. Your guess is as good as mine.