I would think that with the daily price fluctuating so much it is too high of risk for online stores to accept bitcoin. Prices would have to adjust with the ticker price of the bitcoin market for it to be safe.
I don't think so.
Most businesses that accept bitcoin do so in a way that near-instantly converts to fiat, so it doesn't matter what a bitcoin is worth.
Those that hold bitcoin themselves tend to be bitcoin enthusiasts.
And bitcoin enthusiasts know to HODL.
In my opinion the price of bitcoin doesn't matter to businesses. Only the public image. When people stop paying for things in bitcoin or talking about bitcoin, that's when businesses who have already implemented bitcoin payments will pull it.
That or if it becomes illegal, obviously.