It's tough to say. Checking the demographics of Ukraine, with the western half being so pro-EU, maybe he's just taking the initiative and securing what territory he can. It's obvious that the Western half of Ukraine will not be accepting Russian rule, but the eastern half seems decidedly pro-Russia, and that includes Crimea. I doubt those on the Western side will ever be organized enough to take territory from the Russian military, and with no western intervention there's nothing really stopping Putin from keeping what he's taken.
It's possible. I can't say that I understand the place very well. Perhaps it could be a replay of South Ossetia. However, I wonder if Eastern Ukrainians would want Yanukovych, or if they would prefer Russian rule over keeping with the Western half of the country.
Well, regardless of anything else it's important they keep their influence in the black sea, so at the very least they -need- Crimea to keep access to their port in Sevastopol, as I don't think the new Ukrainian government would allow them anywhere near it following a withdrawal at this point. Because of this, territorial claims are definitely part of what they're looking for. Possibly in the form of an independent Crimea ala South Ossetia, or what seems more likely at this point full integration of Crimea into the Russian federation. I say this is more likely as Crimea already voted for independence before Russia stormed in and took their parliament over, soo... yeah.