There's an analogy I like to use... you're baking bread. Bread is just flour, water, yeast, and salt, plus maybe decoration ingredients. You mix things in the correct proportions, let it rise, bake at the right temp/time, and you get bread. Easy, right? Then someone wants you to put in raisins. "It should be easy! It's just a handful of raisins, I don't see why you're telling me it can't be done!", they shout, five minutes before the oven timer goes off.
Scrum is, at heart, designed precisely to stop the behavior you're demanding - that is, the endless stream of "small" interruptions and constantly shifting priorities. The raisins.
Why are you trying to "shoe horn in work" for this iteration that you weren't aware was even an issue when the iteration planning happened? Is production down? Is it a hair-on-fire emergency that threatens the business? Or is it just "important". FUCK important. If it's so important, put it in the story backlog and have it done in the next iteration.
If it's important enough to disrupt the iteration, it's important enough to cancel the iteration, toss all that iteration's unfinished work onto the backlog, and start over. That's how Scrum is supposed to work, but never does, because someone wants raisins at the last minute and thinks it's not a big deal.
