I think we have some pretty good discussion of this question already from earlier Questions 729, 1497, 1806, 2111. It's a fascinating question certain musicians and artists have raised through their work (just as you imagine), and all the more interesting for there being no compelling way of reaching an answer.
1. Yes, there is much interesting philosophical work on modern art. I would start with Arthur Danto, who has written many interesting essays (often for the Nation) and a few fascinating books on the topic.
2. The term aesthetics is certainly applied to music -- see Theodor Adorno and currently Lydia Goehr and Peter Kivy for example -- as well as to poetry. Less frequently to literature, but this is presumably because there aesthetic quality is typically a less important component of overall quality (esp. outside fiction).
3. "Logic" is perhaps not quite the right word for what you have in mind here. Perhaps "rules"? I would think that aesthetic judgments are intuitive judgments, and that any rules laid down for composition or appreciation have standing only insofar as they are confirmed by intuitive judgments. (Intuitive judgments may differ, as they did in respect to the atonal works of Arnold Schönberg, for instance, and judgments about rules will then differ correspondingly.) To what extent can our intuitive aesthetic judgments be expressed in rules? This question has been quite interestingly addressed in modern times by reference to the apparently quite fundamental distinction between objects that are and objects that are not works of art. Is there a rule for drawing this distinction? Marcel Duchamp raised this question dramatically when, in 1917, he took an ordinary white gentlemen's urinal, called it Fountain, signed it, and put it on display. In 1962, Andy Warhol began displaying Campbell soup cans. The debate about what is art, and what is good art, is ongoing; and Arthur Danto's work offers an excellent entry into this debate.
Terrorist acts can be considered art, surely. I know an artist who, when he saw the WTC burning from his loft window, thought this was art (namely the filming of a movie). But his judgment was based on a factual error. So you might ask: What may rightly be considered art? I think the best answer to this question now is that there is no good answer, no boundary between art and non-art (see my response to question 865). To be sure, we might consider in very bad taste an invitation to consider as art a terrorist attack in which innocent civilians died. But much of what is treated as art (exhibited in museums, sold in gallaries) is widely considered to be in bad taste -- and defended as expanding the consciousness of a complacent public. And similarly for other properties that one might think disqualify something from being art. For any such property, or combination of such properties, there seem to be things with these properties that are considered art.
This revolutionary question was raised in a different way by Andy Warhol when he first painted Campbell soup cans (around 1962, I believe) and especially when he displayed Brillo boxes in gallery and museum settings (these were commercial wholesale boxes containing little steelwool soap pads for use in cleaning pots and pans). People asked what he presumably meant them to ask: Is this art? And how does one tell (properties of the object, intent of the presenter, setting and context, or what)? There are different responses to these questions. One of these is that the very distinction between art and non-art is untenable -- or, perhaps better, has been subverted by the evolution of art itself. Some wonderful philosophical reflections on this theme can be found in the work of Arthur Danto. See e.g. his "The End of Art" (in his The Philosophical Disenfranchisement of Art) or The Transfiguration of the Commonplace.