For what it’s worth, here are my thoughts on some of the topics raised.
1. I agree that the idea that “everyone” gets a happy ending applies only to the main characters. Obviously, there’s no way to give a happy ending to the guy Rumple turned into a snail, or to the villagers massacred by Regina, or to their loved ones. Not even all the regular characters will get a happy ending. Neal didn’t. Graham didn’t. There may yet be more losses.
2. I suspect they are going to be more creative in how they dish out happy endings than most of the fan conversations seem to imply. Remember, we’ve been told repeatedly, “Your happy ending may not be what you think it will be.” This avoids the problem of what seem to be mutually exclusive happy endings, e.g. Marion vs Regina. One of them doesn’t have to “lose” in order for the other to “win”. It’s quite possible that Marion or Regina or both could find a happy ending without Robin.
3. On a related note, I was glad to see that Sunday night’s episode seemed to be somewhat defusing the whole idea of a Marion-Robin-Regina triangle and instead gave us a Robin Hood who made the honorable choice while giving us Regina’s disappointment as an opportunity for more struggle and growth of her character. She was clearly tempted to fall back into her old habits but managed to resist in the end and save Marion. I think her story remains interesting so long as she continues to take two steps forward and one step back, which provides a mechanism to study her character.
4. I don’t think Emma is at fault in any way. She saved an innocent woman’s life! That’s a good thing. Period. If that causes an inconvenience to Regina’s social life, that’s a pretty trivial price to pay. I don’t understand why almost everyone is assuming the Star Trek model of time travel in which changing the timeline is a terrible thing that must be avoided. There are plenty of other SF stories in which changing the timeline for the better is the main goal. When we’re dealing with a fictional activity like time travel, we don’t have to be bound by one particular interpretation of it which says there is some “Fate” that shouldn’t be changed.