I think most of Crimea actually does not want to separate, but that's just the impression I get from talking to people. I wish there was a way to find out the real numbers.
I'm in Poland but there are lots of Ukrainians here. I might be getting the wrong impression because i'm talking mostly to young people but it looks to me that the russian-speaking part of Ukraine is not as pro-russian as the media is portraying it. Most people i've talked to so far say things along the lines of "My first language is russian but i'm ukrainian. We have our own identity and even if the country is in a shitty situation, no way we would like to be annexed to russia". When I asked my friend about Crimea, he said he's been there in 2010 and locals he was talking to were complaining that russia was giving out fake russian passports and pushing for a pro-russian view. On top of that, Crimea still has a Tatar population and ethnic Ukrainians that are definitely not pro-russian. It's hard for me to believe that Crimea wants to separate when everyone I talk to tells me the contrary. I'd like to know what the numbers actually are, but I would guess it's probably split around 50/50.