A Dragonbreak occurs when a guardian of Time, Space, or Continuity dies or otherwise messes up.
In theory, there is no limit to what a Dragonbreak could potentially cause, because it can mess with continuity in addition to time and space.
Another issue that you never really got back to me on was whether or not miniature Dragonbreaks could be induced in the HP universe itself (such as an alternate version of Harry accidentally doing something with a Timeturner and that being the cause for why and how another version of Harry could end up here).
It could, though Dragonbreaks. . . well, I shouldn't say that. After all, it may be impossible for TES mages, but time travel isn't impossible for HP wizards.
It could, but I don't think it's likely to happen. Not unless it creates a huge paradox or reality bork. I say that, because a Dragonbreak is referring to a
specific event, which is the breaking of one of the great dragons that maintains reality.
Since timeturners don't affect them, I would not call a timeturner-related paradox a Dragonbreak. Not unless it was a
huge paradox. One that somehow caused a cascade failure that
resulted in a dragon breaking.
Also, in reference to the above, you
can justify a Dragonbreak doing things that extend beyond the Sphere, because it's the dragons that
maintain the Sphere, and keep it where it is and working the way it does.
If one of them broke, the Sphere could potentially change it's shape, dimensions, or even cosmological position. A Dragonbreak could easily cause a part of the Sphere to ram into the Starwarsverse, even while another part pierces into the Touhouverse and Narutoverse, and yet another folds into itself and creates a time discrepancy, which itself then fragments out to affect all the other universes the Sphere has collided with.
Dragonbreaks are Serious Business in every sense of the word. They can have permanent, far reaching consequences, and are capable of causing havoc on an omniversal level.
It's bad when a universe's keystone cracks or shatters. It's even worse when the act can potentially turn the entire omniverse into a giant tenth-dimensional pool table, with the Sphere acting as the breaking shot.
(
Buckle your seatbelts, ladies and gentlemen. This could be one HELL of a ride.