"When" used as a conjunction does not usually imply sequence; it usually means "at the same time." It can be used to mean "immediately afterwards," but it's used in order to focus on the immediacy. So He said to me his name when I gave him the money is emphasizing that "as soon as I gave him the money, he told me his name."
"Knowing" is a state of being; you learn something at one moment, and then you know it for a long time. "Know" is rarely used to describe the moment of learning something. So when I met him, he knew the news would usually mean "at the time that I met him, he already knew the news." It would usually not mean that he learned the news at the same time as, or immediately after, meeting me. If that's the meaning you intend, you could use "learned of" in place of "knew." If you instead wrote "when he met me, he knew the news," then I would assume that *meeting you somehow instantly informed him of the news (as would be the case, for example, if the news was that you are visiting from out of town). This is because the focus is on him, so the implication is that it affects him somehow, so I would assume "know" is being used like "learn." (2b) should now be clear: It means "at the time when I met him, he did not yet know the news."
He lived in Germany when I arrived means "at the time when I arrived, he was living in Germany." If you used the past perfect ("he had been living in Germany"), it would mean "at the time when I arrived, he had been living in Germany [for some time already]." The implications are slightly different, although in most situations either would fit. English speakers often choose the simple past instead of past perfect when the context in unambiguous, just because it's "simpler."