The Parable in the early part of Luke 20 is once again not a parable that Jesus precedes with "The Kingdom of God is like..." but I think the parallels in this case are too obvious to not assume that the landlord in the parable is representative of God, if only because he sends his son who is killed. Now while the SAB calls the story violent, and I can see that, the injustice label is a little more questionable. These guys who are taking his property have also killed his son, so it's not that surprising that the landlord reacts with violence.
The little story in verses 22-25 are not universally recognized to have the meaning that the SAB appoints to them, but I happen to be in agreement. I think Jesus is definitely saying that people should pay their taxes, and it's not a great stretch to suppose he's suggesting a separation of church and state. (Note that Old Testament laws stated that a man could be a king or a priest, but not both.)
The argument Jesus has with the Sadducees in verses 27-38 is an interesting one, as the Sadducees didn't believe in life after death, and they were trying to set out a ridiculous scenario to confuse Jesus. The general understanding of Jesus' reply is that in the afterlife, there won't be marriage, so the question is meaningless. Is death final? I'm sure I've answered this many times, but no, death is not final, in the sense that when someone dies, they move on to another stage of existence. The SAB suggests jokingly that "Dead people have no God" but it's more proper to note that there's a certain sense in which there are no truly dead people, as their souls last eternally.
Jesus' little speech in verses 41 to 44 is a bit cryptic, as he seems to be claiming that he's not the son of David, even though that's a title he has willingly been referred to in the past. I'm not sure what his point is supposed to be unless perhaps it has something to do with the virgin birth which honestly is not spoken of much in the gospels.