Are you sure? Doesn't seem right to me. If the jury has decided that he is innocent on count no. 3, then the judge certainly couldn't vacate that finding.
Nope, I'm not.
I know that double jeopardy attaches if the judge accepts the verdict on the one count. I also know that acquittal on one count does not preclude retrying on the other counts.
I was thinking that there was a recent court opinion to the effect that double jeopardy does not attach if a mistrial is declared before the verdict is read, but this is not an area in which I have any expertise so I could be misremembering it.