I think I'm going to be a little disappointed in myself when it comes to chapter 18, as the SAB opens with a question that I don't think I have a good answer for, even though it seems like it shouldn't be a tough one. Is it a good thing to be childish? I think it's quite clear from the number of times Jesus makes this statement that being like a child is a desirable state. However, it's also clear that Paul is teaching childishness is bad. As I said, I don't know the resolution of this issue, but I do think I can shed some light on possibilities. You don't have to be a theologian to recognize that there are traits common to children that are both desirable and not. Children are very trusting, full of energy, and generally cute. At the same time, they are ignorant, weak, and prone to temper tantrums. Perhaps the Bible could stand to be more clear on what it means when it compares us to children, whether negatively or positively. The one thing that Jesus does specify here as a positive trait is humility, which is certainly something that young children are very good at, and I could see being a positive trait for a Christian.
I don't think that Jesus is condemning the whole world in verse 7, but rather making an observation that the world is full of bad things. And as I said back in chapter five when similar things were said by Jesus in the Sermon on the Mount, I think verses 8-9 are hyperbole.
The SAB asks whether God can be seen. I addressed this in Genesis 12, but I think this verse is a special case, because it's talking about angels rather than human beings; I don't doubt that angels can see God.
While the note on verses 15-17 is talking about JWs, which would usually mean I don't care, it's on a noteworthy subject that I might as well address. I think that the Catholic church and the Jehovah's Witnesses have both been excellent examples of how not to deal with child molesters. While I could possibly imagine that there might be an acceptable way for these organizations to deal with such troubles internally, the fact is (as far as I am aware) both organizations have simply not dealt with the problem at all. And after all, in the end, it's turned out to be counter-productive if their main aim was to avoid shaming themselves. Anyway, child molestation is a serious crime, and it should be dealt with severely.
In verses 23-35 Jesus tells a parable about a king and a debtor. The SAB has problems with this parable, and while I understand, I think it's worth mentioning that it is only a parable, and as I said a few chapters back, you can't always take parables quite at face value. Just because the parable involves torture and slavery doesn't immediately imply that Jesus is coming out in favor of those things, but it does say at the end that people need to be forgiving or they will miss out on being forgiven, so take that however you will.