'Safely' is a relative term.
He can 'safely' call up that power in that it will cost him only a single mental stress to do so.  Whether he can then control that power without having to resort to backlash or fallout is another matter, and one that is in the hands of the Dice Gods, though the odds are not in his favour.
It is hypothetically possible for any character with channeling or evocation (or a sponsored version thereof, for that matter) to create a rote of an arbitrarily high power level.  The spell being a rote merely means that the character is assumed to have rolled 0 on the dice for controlling the power.  If that's insufficient to the power they called up, well, good luck with that.

Possibly.  Though given the number of oddball, disparate, and down contradictory beliefs people can hold I'm not sure knowledge of what's going on is really needed. 

Question though, do we want to delve into such a min-game creation here?  We may have derailed this thread enough...

Also, I have a digital copy of that one, MBuzzard... and there's another one that's got a few bits that skipped by the editor. They're quite funny. I could probably be convinced compile them for your enjoyment... so far as I'm aware, it's not copyright piracy to share a clip (or boy, is YouTube in trouble).

There's an audio book that shipped with something that should have been edited out.  Well, with a couple of things that needed editing, but at one point Marsters is faced with a latin chant and says something like: "Well how am I supposed to pronounce that? Hell, does anyone want to wait for a couple of hours so we can get a latin speaker in? No, that would be stupid.  I'll just pronounce it BLAH and sound confident and only latin geeks will know if I nailed it or not."
Then goes back to reading, pronouncing it BLAH and making it sound as if he knew what he was saying.

In short - you can't always trust the audio books for pronunciation.

Richard