"Then why would it make you sad to provide a family member or loved one with that terrible job"
It would also make me feel extremely sad to not give them money with no strings attached if they're in need. What's the point? Are you saying that it's unethical to not give your money to family?
If they needed the money, I would feel better getting them to fight for it (because after all, that's better than them dying of cancer or whatever the money is for!) than I would not giving them the money, but I'd feel bad in both situations, because all I'd want to do is maximally help them, and either of these options isn't that.
"I think if everyone acted according to your principles, there would be a net gain in human misery."
That's funny because I thought the same about your views. There are people on the left that want to shut down trade with China or Bangladesh because they view low wages as exploitative. They would condemn these people to the outcome of poverty and death because of their ad hoc ethical rules that have no grounding in outcomes.
"If I had realized you thought it was literally impossible for any employer to behave unethically toward an employee"
I said the opposite. Look at my list of assumptions. In those assumptions are all the typical violations of the employee to employer power dynamic, such as unexpected surprises after the contract is signed (say, unexpected occupational hazard, whatever), deceptive fine print in the contract, pressure tactics to get them to agree to something they don't want to, and so on. That's hardly a Randian perspective. Rand thinks none of these things are possible because people are rational creatures that will never agree to something that isn't in their best interest.