So, this is a basic misunderstanding of gravity and acceleration. The measure of Gs is the exact measure of how fast the acceleration is.
This is just like asking if it would be comfortable to survive 100 C if the temperature was cold enough.
There is no difference between acceleration and gravity. If locked into an elevator, you wouldn't be able to tell with certainty if the elevator started going up, or someone had just turned the gravity of the planet up to make you heavier somehow. If the elevator suddenly dropped in freefall, you would not be able to tell if it was the elevator moving down, or someone had simply turned gravity off somehow. This is part of Einstein's Special Relativity.
Yes it is possible because it has happened. I'm not an expert, but I believe survival rates are connected more to duration than G force. If the body becomes unable to circulate blood and regulate itself for a long enough period of time, it dies.
That's exactly what happens. The human body cannot withstand more than 2-3 G for a prolonged period. Above that, the heart just can't pump blood and you die if you stay there too long. For instance, Stapp, the world record holder only withstood 46.2 Gs for a brief instant. Normally your blood weighs about 8-10% of your total body weight, so for the instant he was at 46.2 G, he weighed about 7700 lbs and his blood weighed between 616 lbs and 770 lbs.
