Not quite.
Firstly, in your example, the character only has a one shift control deficit. This means the spell costs the standard one mental stress to cast (it's equal his conviction), but he'll default to suffering from his choice of 1 point of backlash or fallout, because he counts as having missed his roll by one. However, you always have the option of spending Fate to invoke an aspect on your control roll, which in your example would bump the imaginary roll over what was needed to control the spell, therefore you would not suffer backlash/fallout. This is noted on YS258:
"Finally, keep in mind that you can have a rote that’s more powerful than you can control with a Discipline roll of zero, which would basically cause automatic fallout or backlash when used unless you can invoke some aspects to make up the difference."
Note that you are still making a Discipline roll to target the spell, which affects damage, and your Fate point would still increase the targeting part of the roll, too (just like it would if you weren't using a rote).