I do remember that she feared him immensely and that he tied her at the end but extensive physical abuse I don't recall. Maybe I'm mistaken, it was quite a while since I read the book the last time.

In the country (as opposed to the city) everybody knows what everybody's doing, there are always a ton of witnesses, who went to whom, who sleeps with whom and so on. If Sir Henry died anywhere near the Stapleton house let alone in it, the latter would be the primary suspect and even the lack of evidence due to rudimentary forensic expertise in Victorian England mightn't be able to save him. And sure the truth that Stapleton is Baskerville would be uncovered and after that any body of jurors would send his ass straight to the gallows.

As for the trouble of using the dog, see it that way: it worked once, it may well work twice, makes perfect sense.

He came to Devonshire already planning to acquire the estate one way or the other, that is why he introduced his wife as his sister. He wasn't sure of the actual method yet but then he had heard about Sir Charles frail heart and his belief in the hound.

When Henry appeared he decided to try the same method since it worked for the first time, that makes perfect sense.

Also, I'm not sure about constant beatings, where did you take it from?

In Anna Karenina Levin and Kitty line is pretty romantic and ends in a happy marriage. Sure, there are a few unsuccessful romantic lines there, but they can be happily ignored.

Too late, bro

Anna Karenina, obviously.