Can a divorced and remarried Catholic receive communion on a case-by-case basis, and did Amoris Laetitia settle it?

Not that I know of, and my guess is that Pope Leo would not disagree with Pope Francis; the only way to know is to go to your priest or write your bishop. But you should know there is a real controversy here. Pope Francis, wanting to be pastoral, slipped past the doctrinal question, which is the old mercy-versus-justice issue: does the Church have the right to be merciful by letting the justice part of the doctrine slip away? Some say it is not ours to toy with, because there is a reason the law was given; others point out that Jesus surprised us with mercy, as with the woman caught in adultery. But notice that He did not simply excuse her; He was seizing the chance to expose the Pharisees' hypocrisy with 'let him who is without sin cast the first stone,' and only because they were guilty of hypocrisy did He have the wiggle room to let her go. If there had been no hypocritical Pharisees, and the question were simply whether a woman caught in adultery by witnesses should be stoned as the Mosaic law required, it might have gone the other way, because making her release the precedent would upset the law and make all the women stoned before her seem to have suffered in vain. So the balance between justice and mercy is enormous, and it is heightened by the fact that a divorce may have happened thirty years ago; justice is justice and law is law, but circumstances change, and it may be time to put some mercy into the justice formula. The only one we have put in place to decide how much mercy and when is the pope, not you and I; if he decides and is still guided by the Holy Spirit, it has to be taken seriously because he speaks officially for the Church.