Loose Bolt

The Faith has millions of followers and there are thousands of septs, septons and septas. So in my head canon any king should be at least nominally follow the 7. In fact if king is not that anyone who either does not like policies of Bran or want to become king himself would have very good excuse to rebel.

I assume that great names are either titles or brands. So when lucky and victorious warlord had wiped out all males that used great name he just started to use that name and after couple generations anyone just forgot that new Arryns, Lannisters and Starks were not really relatives of their nominal predecessors. And that has happened many times. Or great houses really belong as many dynasties as Pharaohs of Egypt.

In my head canon major reason why Stannis became Lord of Dragonstone was to make sure that potential supporters of Targ are kept under control. After all most of houses sworn to DS were loyal to Targs and some of them even are very distant relatives to that ex royal house. So Robert needed someone who was both strong enough to rule them and loyal to him. Or there is no way that he would allow young and possible sick girl inherit DS. Besides another thing is that Dragonstone was seat for crownprince so it is possible that lordship of DS is not even inheritable. Or Stannis gained his seat for life. But in case of his death King of Westeros would have hired new Lord of Dragonstone.

Shireen is young female without any VIP who would support her claim. When Joffrey and Tommen are grandsons of Tywin and their mother is queen and hardcore bitch. So if Stannis had died b4 beginning of SoIaF Lannisters would have made sure that either Joffrey or Tommen would inherit Dragonstone. In fact I would not be surprised if Shireen had either disappeared or had fatal accident.

If Stannis died without having a son there is a possibility that DS would go to Tommen. After all Tommen would have more support than Shireen.

One potential reason might be that Glovers and Tallharts are "only" masterly houses. Or heads of those houses are not lords.

Could objects made of VS have their own will and magical abilities? After all almost certainly they include blood and souls of sacrificed people that were used to make VS and there is even a chance that they will drink some blood and eat souls of people that are killed by them. So there is a possibility that Longclaw had become metallic weirwood and has gained ability to communicate with people via their dreams. Or reason why Jorah gave LC to Jon was that he thought that Old Gods, but really Longclaw, wanted that to happen.

By using Bridge of Skulls anyone could bypass the Wall.

Ramsay has eyes of Bolton. In fact those eyes saved his life when Roose saw him as a baby. A Dance with Dragons - Reek III

Starks and Tullys became enemies of Targs when they rebelled and so lost their right to rule their lands. So if Dany comes to Westeros soon enough Boltons and Freys could turn their cloaks again and become her bannermen. After all she will need somebody to rule North and Riverlands.

????

Wildfire might work.

May be same reason why House Whitehill had been bannermen of Boltons 500 years though they live closer to Winterfell than Dreadfort. But only source that mentions that fact is the game. After all House Whitehill might not exist in the books.

I assume that partly rule of cool and partly bc certain players in main series (like Baratheons and Lannisters) had to survive the Dance. For instance if Rhaenyra would have nuked Storms End as soon as she found out that Baratheons supported "usurper" and made sure that everybody would know that she and her dragons would do the same to all property of any "traitors". Or she would have burned down Lannisterport and Old Town if Hightowers and Lannisters had supported another candidate for Iron Throne. The Dance would have included only one battle. Because Aegon II and his brother would have either had to launch air raid to Dragonstone and hope that they could kill enough hostile dragons and their riders or they would have lost everything bc their supporters almost certainly would not have dared to openly support him as long Rhaenyra had ability to carry out that threat. Or if both Blacks and Greens had been smarter the Dance would have been shorter and most victims of that would have been dragons and their riders and some unlucky people who just happened to be either in Storms End or Dragonstone when dragons danced. But story about the Dance would have been shorter and less cool.

I suspect that Ghost used Bridge of Skulls.