Your questions are valid, but you have to realize that they are not the gotchas that you think they are. Socialists - who are the ones advocating for socialized production - have been writing books providing elaborate answers for your questions for over 100 years. Those socialists have thought long and deep about those problems and if you haven't you should listen to what they have to say. Like, someone who has never written a line of Lisp in their life should first learn the language before stating that it is impractical.

Your first question assumes that jobs can be ranked on a shittyness scale. This is true in a capitalist society, but why is it true? Why is developing software at Microsoft less shitty than frying burgers at McDonald's? Is the act of frying burgers shit and the act of typing source code on a computer less shit? Is walking dogs more shit than lecturing at universities? The answer to these questions are no, or else people wouldn't fry burgers at home and they would not buy dogs.

The shittyness of a job is more dependent to the employee's circumstances, like how much autonomy they have, their social standing, job security, treatment by others, etc, than the actual tasks performed.