Unfortunately, rallies organized and comprised of people who just lost the election will not convince the Trumpenfuhrer or the GOP-controlled Congress to change their minds on this. Something something "liberal babies want handouts! Sad! Get a job! Don't die!"
We're going to have to play this in a sort of depressing fashion: let the Republican and Independent Trump voters who opposed the ACA lose their healthcare, get extremely ill or die, and watch as the GOP is burned at the stake for this. If it even comes to that. Depends how much people are willing to accept the narrative that Trump frames. He could just say that Obama ruined healthcare reform prospects with the ACA and that results won't be noteworthy for many years. Knowing the alt-right, they'd believe him.
I disagree. If we get more and more people rallying against the Republicans and their sick plans, they will be forced to change their positions. 2018 will be a tough year for them if they don't.
One thing I will agree with is that singlepayer won't happen as long as Ryan is the Speaker because he's too much of an ideologue. So we either win the House or at least beat him in his district.