Is that a good estimate according to your posted poll?
Less than that, since, even of that minority that did not say they favored separatism, part of those are on the fence, and they're probably even more on the fence or outright opposed now after having a couple of months of kidnappings and random killings by the Russians. The Pew poll I posted to you a moment ago was from April.
"So despite the recent unrest caused by pro-Russian militias in eastern Ukrainian cities like Donetsk, Luhansk, and Slovyansk, only a small minority of Ukrainians in that part of the country want the right to secede — 18% overall, and only 27% of Russian speakers."
From same link as before
From what I have read about people writing from the area it is less now. Russian propaganda TV had a larger influence on them when it was blasting lies about supposed horror in Western Ukraine and Russia as savior of the East.
When the people saw the things militants did and how the same Russian TV was lying about what happens in their own neighborhood (i.e lies about Ukrainian soldiers gathering all town to witness how they crucify a toddler) then more people saw very clearly it is not to be trusted.