How realistically possible would it be for Ukraine to move the date of the Referendum back(by negotiating with Russia) or interfere with it to keep it stalled until a proper Ukrainian Government has been elected?
I think we're past that point, pretty sure Putin will make sure the referendum goes through. Elections in Ukraine would be difficult now, with Crimea in Russian control and unrest in some predominantly Russian-speaking cities like Odessa and Donetsk.
I'm afraid at this point we're negotiating about what happens with the rest of Ukraine. The Russian Foreign Ministry has released a statement today accusing the Right Sector of being responsible for the unrest in Eastern Ukraine and some other stuff, and the government in Kiev of tolerating it (
link in Russian, got that from
here). Remember, Putin has a mandate to intervene in Ukraine if Russians are in danger, which is pretty much what they are saying right now.
Russia still does not want to participate in the proposed contact group and still refuses to talk to the Ukrainian government. I guess the plan is to push the referendum through, then the EU will issue sanctions which ideally should force Russia to talk with Kiev and come to some kind of understanding. I guess they will want to keep Crimea after the referendum though, that seems difficult to prevent now.