1)- which begs the question, why wasn't this done with the other ships as well?
2)- this is true, but not relevant to the questions asked
3)- We don't know this, and it makes little sense considering the rebels won at the end of ROTJ and formed a New Republic and the Empire was scattered to the Outer Rim. If anything, the Rebels should have better ships, however, I can understand why you think the rebels have trouble getting ships, as these new movies have really painted the FO as a powerhouse while providing no context to backup their position. I suppose your comment is canon accurate, which just means the canon is confusing
4) This makes no sense and seems to be a narrative people are pushing to wave away one of the many problems with this scene. In a universe where a ship can destroy another ship 30 times its size by going into hyperpace, every competent captain in every battle would fear for the safety of their crew whenever another ship is pointed at them. Whether or not there are life forms on board would be irrelevant, because there are clearly droids in the universe which are capable of hyperspace jumps (this is the purpose of astromech droids). Plus, given the destructive potential of this maneuver, it would be immediately weaponized, thus missiles would be equipped with hyperdrives rather than firing proton torpedoes. As far as I'm aware, the narrative that Holdo had to be on the ship to trick the FO is something invented by a fan in defense of the scene and is not supported by anything in the movie (do they scan the ship for life in the movie?). Hux doesn't even seem to think this maneuver was a possibility until it's about to happen. You'd think any craft with a hyperdrive would be considered a deadly missle if this was possible
A better response for TLJ apologists to the autopilot question would be "Why aren't all space battles performed by androids"? We see how much better BB8 is at wrecking up a scene in an AT-ST than any Imperial pilot has been, and that's just one example. It's an easy whataboutism to muddle the complaints people have about Holdo's sacrifice, but there is a legit response. Like weaponized hyperspace, drone piloted ships break the rules of the universe. In theory, a drone would be infinitely better at piloting than any humans for the same reasons that self driving cars are going to replace humans. Star Wars space battles are modeled after WW2 dogfights so human pilots can have human moments that the audience can enjoy. The technology is nerfed specifically to service the story (which is what makes this more space fantasy than sci-fi)
Bare in mind that if Holdo had simply rammed the Supremecy, few people would be bringing up auto pilot. It's the fact that the rules of the universe were broken that has precipitated a bunch of other nitpicks about the scene, i.e. the writers thought they were clever by subverting the rules, now the internet trolls will show they are clever by doing the same. It's a can of worms the script of TLJ has opened and will have to deal with
5)- which the FO figured out anyway, not sure what this has to do with the original question