The answer to the first question is related to an interpretation of David Hume known as Hume's Law, paraphrased as, "you can't derive an ought from an is". In other words, the results of science cannot tell us anything
conclusive about ethics/morality or what we should do day to day. The submission contained the following quote regarding neuroscience from a well-regarded paper: "it 'can help us see that all behavior is mechanical, that all behavior is produced by chains of physical events that ultimately reach back to forces beyond the agent’s control.'" Some pretty drastic changes to the rule of law could result from equating such results with "there is no free will". How do we decide what
ought to comprise such changes? Secondly, as exhilarating and awe inspiring as learning the results of science can be (for me at least), how do we take knowledge and do anything with it? We can use it for technology, sure. But what if tomorrow we conclusively determine there are extraterrestrial beings through the results of one of our scientific instruments? How does society respond in relation to what the discovery means to each person despite the fact the experiment says nothing about such meaning? You could also think of it all this way: what
ought we to do once we know every possible provable (or Popperian falsifiable) statement about existence?
As for the second question, to me, it makes sense that there has to be a lowest level of ontology, unless the lowest level is some sort of recursive structure (which in a sense would still be a "lowest level thing"). I believe most of us expect that there is some sort of monadic entity that is equivalent to Democritus's atom. In the standard model the quark is that sort of thing (if I'm not mistaken), but the string theorists hypothesize that a lower level (think more complete, i.e. not assuming zero dimensional entities in reality) object is the basis for a quark. Or say, if we can somehow determine our universe is a simulation, then it would be nice to know what the "basement universe" that is running this universe is. Of course, it's possible such knowledge will remain forever inaccessible, in which case, we'll probably need novels and philosophy to deal with the voids left in our hungering minds.