I said nothing about polls. What I did say was that last time the opinion of Crimeans was gauged in a referendum was 1991 and the result then was that they were 54% for independence from Russia (then represented by the Russian Sovier Federative Socialist Republic, RSFSR). 42% were against independence. The turnout was also the lowest in Crimea at 60%. That was the closest, but still a clear win for those favoring independence. Similarly, ethnic Russians favored independence at 55%. Ukrainian independence referendum, 1991.
if Ukraine fixates on Crimea, it will lose everything
What the Ukrainians do and on what they fixate is up to the Ukrainians. It is rather evident that the energy to fight for Crimea is not there; however it doesn't make the annexation right. The likely scenario is that Crimea will become like these other acquisitions of the Russian Federation: Abkhazia and Osetia, with an indeterminate status and underdeveloped economy. RF will lose all the prestige it struggled to accumulate for the past 20 years. The best for RF would be to leave Crimea voluntarily and set up another Crimea referendum with observers and with cooperation from Ukraine. That is likely to result in a legal annexation; and at the same time that will allow Ukraine to safeguard true sovereignty, including whichever alliances military or economic it wishes to join. But RF is not likely to have the wisdom to do that.
NATO membership for Ukraine is largely up to NATO. All Russia's neighbors have learned the lesson by now that if they want sovereignty they need to join NATO ass soon as possible.
Do not discard the possibility that RF will invade in the East, either after fomenting a civil war in Ukraine or not. The latest developments show that The Ukrainian Revolution has entered an uncertain phase. So Crimea may very well be a moot point for the coming couple of years.