That study looks at lifespan after reaching 5, and 50 might still be a little generous with the care that humans could provide each other 50,000 years ago. 50 is about the lifespan of a king 3,000 years ago, I can't imagine gen pop faired better.
Me too. We have plenty of bones of people who lived into old age with signs of disability or having been crippled.
But the overall stats not only do I not know, but since we only have a relatively minor number of data points it's hard to really say any of us will ever know.
What we have does tend to point to being better than a medieval city iirc, and I think the general consensus amongst anthropologists is that the transition to agriculture saw a decrease in life expectancy.