If that's true, they're still outliers. This is going to damage Romney heavily.
If you're trying to be a president for all Americans, it's unwise to just write off 47% of the electorate from the start, even if cracking 53% seems unlikely.
The latter is BS. Even in 2008 Obama didn't quite break 53%... I doubt Romney's hypothetical ceiling is higher then that.
I'm skeptical that this will hurt him. His statement was only inaccurate in so far as it ignored Obama supporters that do not identify as victims/entitled to assistance, and almost all those supporters consider other segments of the population as victims entitled to assistance. Most voters won't care for that lack of nuance.
I doubt it will alienate Republican-leaning elderly or lower class whites away from him, because such voters don't identify as "dependent on the government"(I recall their was a survey some time ago that said the majority of people on Social Security, not to mention various other government programs, don't associate those programs with the government).