Not only that, but the whole "survivable" part of G-forces was created for, as you said, /sustained/ periods of time. If you honestly felt the impact that Decker felt for more than .03 seconds, you'd die in a few seconds. Same with linemen.

Charlie Weis/Mark Mangino fat joke!

Also, to point out, it wasn't that hit that knocked Decker out of the game. Dude came back in and proceeded to help score all three of their touchdowns before getting knocked out with an ankle sprain. So he did walk it off.

Formula 1 teams design their safety equipment to withstand crashes of up to 70 G. Why do they stop at 70? Because beyond 70 G, human organs cannot withstand the trauma, no matter how well designed the cars are. Any crash over 70 G is not survivable, period.
Something has to be done to increase safety in football. You can't just "design better equipment", and wrigint rules about player size are unrealistic and unfeasible.
There is, however, one solution that would be effective and would be inexpensive to enact: make the fields bigger. With more room to run, "skill players" can avoid linebackers and linemen more easily, and the offensive and defensive lines would have to spread out, creating a wider pocket.
Larger and slower linemen wouldn't be able to keep up, so smaller and lighter players (10-20 pounds) would emerge. With less mass and less velocity during collisions, the number of injuries would go down. The smaller players would be faster, but because more collisions would be east-west, not north-south, the number of direct high-G impacts would be fewer.
Just widening the filed by five yards could make a huge difference in safety without compromising how the game is played.

Carl V is right. And comparing gravitational accelerations across scenarios isn't really a valid metric to begin with. G is not force, it is acceleration. For instance, I think that beebee guns have accelerations upwards to 10 G, and a beebee would barely break your skin. Granted, football players weight more than beebees, but to have sensible metrics for comparison, one need weights, impact times, area impacted, probably actual velocities as well, etc. Having said that, the professor is probably right on his gravitational acceleration calculations. but there is a host of other information that is needed in order to appraise "safety" effectively.
Don't get me wrong, more safety in football may be needed, but you cannot simply compare G's and call it good.

Minnesota physics prof? Puh-leeze. Dr. Dahlberg is like the Gordon Wood of the physics world. Amiright? Dahlberg drastically underestimates the impact of Sean Cattouse predicated upon Eric Decker.
I took a physics class at Berkeley (it wasn't between recess and lunch) and let me tell you that [profane] was insanely hard. Long story short, I dropped it and no one was the wiser.
TENURE! TENURE! TENURE!