I'm familiar with these (and others) I just wanted to know which ones you want me to respond to.
The sensationalism of Sinclair's novel (i.e., not
a documentary) is contradicted by the lack of any substantial complaints registered to any of the various inspection agencies responsible for overseeing meatpacking at the turn of the 20th century, as well as testimony offered for several congressional hearings.
As popular myth would have it, there were no government inspectors before Congress acted in response to "The Jungle" and the greedy meat packers fought federal inspection all the way. The truth is that not only did government inspection exist, but meat packers themselves supported it and were in the forefront of the effort to extend it! link
Regarding child labor and the 8-hour workday, the orthodox justification goes something like this: Long working hours & child labor, although objectively bad compared to today's conditions, represented an improvement over prevailing working conditions in that era (echo similar arguments today, to the sustenance farmer who is barely feeding his family in rural China who takes an offer to work for $1/day making Nike shoes).
I'm going to meet you halfway and say that this is probably as much pipe-dream/rationalization as it is based on factual history.
However, it is not accurate to suggest, as you have, that either of these arose under anything even remotely resembling a "free market". For example, when corporations hired Pinkerton guards, agents provocateurs, and strike-busters to abuse laborers exercising their right to assemble in petition for better working conditions, when these same corporations encouraged their cities (Chicago, a prime example) to build federal armories to safeguard against future Labor organizing/protests (in Chi-town I believe this was a direct response to the Haymarket Riots), is all evidence of a decidedly unfree
market, one where Capital rigs the game in its favor, enlists the government to help where it cannot win on its own, etc.