This is very important work, Adria, and you are totally on the right track. A few questions:

1. What does "ideological terrain" mean? Do you need to disaggregate this concept into, say, legal scholarship, judicial opinions, politicians, academe? I am still puzzled at the skepticism about free speech that has sunk into far-left (I don't know what the right word is) circles since the 1980's--partially MacKinnon/Dworkin, CLS, the legacy of Marcuse's "Repressive Tolerance, but perhaps also a reflection of political impotence, making it easier to police speech rather than change laws/social policy. We also like a clear understanding of free speech in relation to academic freedom. It is unclear what my free speech rights in the classroom are, for instance.
2. The central philosophical problem is the speech/conduct distinction. But related is the unstable relationship between the religion clauses and the free speech clause (see Rosenberger v. UVA, which conflated public university refusal to subsidize an evangelical student publication with violation of free speech). Hugo Black (I know I'm the only Black devotee left, probably) saw some of these problems in Cohen v. California and elsewhere, when he wanted to draw a bright line between speech and conduct, lest the average citizen get confused about what free speech was. I think the change from speech to "expression" was disastrous in this regard. I deeply dislike Judith Butler's Excitable Speech for a number of reasons but her appropriation of J.L. Austin on performatives is an essential starting point for this discussion.
3. How that relates to your case studies, especially Hempstead, is that not only are we confused still about speech/conduct, but also about reasonable "time, place, and manner" restrictions.
4. Do new media make a difference? The ability of the 'Net to circumvent censorship seems relevant.
5. How "doctrinal" do you want to be in this dissertation--most of the research questions are descriptive rather than normative. I don't know what the right answer is here.

I'm sure I'll have more thoughts, later. Hope this helps.