On Dany's face-heel turn, I'd agree. Her capacity for cruelty has been there for all to see since she burned the witch on Drogo's funeral pyre in the first season. I think that to a degree, people have let it slide in the past because in the main, those whom she burned or had crucified were seen as "fair game". In show, Tyrion and Varys would have been starting to worry about her temperament after her return to Mereen, or when she burned the Tarlys.
What I have seen suggested elsewhere is that her apparently sudden "snap" would have been more plausible if Rhaegal's death was postponed from the previous episode. The idea being that having torched Euron's fleet and the wall-mounted scorpions, the two dragons settle down as the bells ring and then Rhaegal gets hit by a lucky shot from a scorpion hidden on a rooftop. Cue Dany going postal in Arthur Harris/Curtis LeMay style on Kings Landing, and everything goes south rapidly...
Certainly, Benioff and Weiss wanting to wrap up the final two seasons in just 13 episodes created a time constraint - another episode or two in each season would have allowed time for more character-driven writing, as opposed to them trying to tick off plot bullet points in the most expedient manner possible in attempting to get from the status quo at the end of season 6 to the finale as told to them by GRRM. GRRM's character-driven writing style should mean that if book!Dany is going to become the final antagonist (which is possibly being portended by dreams that Dany and Jon have had), her motivations will be better fleshed-out than in the show.
There's a good thread on Twitter that analyses plot versus character-driven writing styles and how that has impacted the adaptation of the books to the show.
https://twitter.com/DSilvermint/status/1125856091261136896Jaime surviving his gut wounds long enough to get to Cersei in time to be buried under the Red Keep is a case of having just enough plot armour, but it's no worse (if anything, it's not as egregious) than Ayra surviving getting viciously shanked in the guts by the Waif - who actually twisted the knife as well - and then diving into what would have been rather filthy water to escape.
Show!Euron is something of a pale imitation/pastiche of book!Euron IMHO, and even the actor playing the part has said that he was hoping to be more like book!Euron.
I'm inclined to think that the long drop into burning ruins/rubble would have been enough to finish off what was left of the Mountain. Qyburns mad science was only really animating what was an increasingly necrotic mess, so the impact didn't burst the Mountain like a piece of rotten fruit, most of his bones would have been shattered, to the point that he/it wouldn't have been able to escape the flames.
Can't really argue on the last two points.