Isn't it the case that in the description of the issue Omega has made enough correct predictions that we should expect that manypeople have had strokes, survived, and went on to make the decision which was predicted

More nitpicking, more absurd fighting against the hypothetical. Omega isn't specified as having made the prediction a year ago, he may have just examined your brain and made the prediction two seconds before he fills the boxes accordingly and presents you the problem. How many people do you expect to have had strokes in those two seconds?

Look, if you resort to "people could have had strokes in the time since Omega made his prediction which would have drastically changed their brain-chemistry", then you're reaching ludicrous attempts of desperation in attempting to defend an undefensible position. Please try to picture how this type of argument looks from an external point of view -- they really don't look good.

Some arguments are so bad, that to speak them is evidence of the lack of a better argument, and if anything strengthen the opposite position.