Dark Matter disk in our galaxy?

Don't worry yourself un-necessarily over this , the earth is very small, and there is a lot more planets between us and the oort cloud, (and an asteroid belt). For one of these extinction events to happen the odds are literally astronomical (no pun intended) It is the equivalent of a sniper shooting the wedding tackle off a flea at 1 mile.

I don't know where you got the figure of 32 million years but yes it could happen.

I don't think dark matter would have any significant effect though.

there is no such thing as 'dark matter' or 'dark energy' for that matter, the scientists have gotten it wrong, quite simply you can't weigh all the matter in the universe as it's infinite and thus there is infinite matter...don't listen to them, they are wrong if anyone of these so called experts would invite me to there lab i'd happily explain their senior school education has no place when determining the answers to the big questions.