We still have a lot to learn of the psychology of the situation. Results from these studies are always interesting. Even if it is far from the real thing.
It is also a perfect starting point for a post apocalyptic novel. "The only group to survive the end was a small band of researchers, stuck in their isolation experiment."
I'm thinking a lot of the equipment is different as well, and since they mention simulating equipment malfunctions, that plays an important part, especially with the additional limitations/simulated dangers.
Antarctica trips have all of those limits you mentioned, they'll just be worse for Mars. While they can operate sort of freely for a few months, once winter sets in, they are just as isolated as another planet. They just get the advantage of easier setup then Mars.
I guess that depends on what you consider reasonable. I figure if they're starting with simulations such as this now, it's reasonable to expect an actual manned mission in maybe 20 years.
Hard to say - There's still a lot of hazards yet to be accounted for: a lot more radiation exposure, literal poison in the soil, severe weather, safe and affordable supply chain, etc.