#2 isn't a serious objection, because the math is pretty clear that almost everyone winds up spending less.
#4-6 are intractable and come down to the population having the will to overcome objections from capital and doctors. I do think that doctors and nurses are gettable if we bring down the costs of malpractice insurance and education so that overall take home doesn't suffer.
In my experience trying to sell the idea, the biggest impediment to real progress is #3, though I am certain I have a local bias. That's the issue that keeps the knowledge working class separate from the labor-working class. I haven't come up with a good answer other than accommodating them by allowing first-class treatment for those with money and second-class treatment for everyone else. Not the most altruistic answer, but probably the most achievable. No one with premium healthcare now is going to risk it, and that's an important political block.