I looked into Logical Chess by Chernev, and the Amateur's Mind by Silman. Any opinions on those?
Book(s) for a 1000 rated player

Good Chess Books for Beginners and Beyond...
https://www.chess.com/blog/RussBell/good-chess-books-for-beginners-and-beyond
https://www.chess.com/blog/RussBell
Hi. Logical Chess by Chernev is a good place to start. My approach is to play through a game 3 or 4 times, then make some notes about one or two key points I liked in the game and want to apply to my own. It's good to look for themes such as how players provoke and attack weaknesses for use weak squares for example. It's a good way to start learning about positional chess. Amateurs Mind is an excellent book but probably aimed at more advanced players, say 1400ish. You won't get the benefit until you have blundering under control and know some basics of positional chess and weaknesses. The key thing is tactics, if you still regularly lose to undefended pieces or basic tactics such as forks and skewers then you need to work on this by doing puzzles daily. This will strengthen your calculation skills and tactical vision.

Yesterday, I got Silman's Complete Endgame Course. The underlying objective of the book is that players require appropriate endgame technique for their given skill, and studying more advanced endgames is a waste of the players time.

Other approaches exist. No one truly knows which way is better. Don’t believe everything you read about chess. Think for yourself. Now I’m not saying don’t believe something a master said just because you think differently. Just don’t read it like a Christian would read the Gospel. That should be said about any kind of writing, especially something religious or spiritual, which are two topics that are obviously beyond the scope of this post.
My aim: I just wanted the reader to know there are a lot of ideas out there. Just because a Master said something, doesn’t mean they are not being paid to sell a certain idea or chess principle.
In short, we all have to do what we got to do, but don’t just pick the first book you hear about. I’m sure you understand this concept, as you where writing this post in hopes people will give you a lot of books to check out.
Think for yourself. Don’t believe anyone, fully...
I think Dan Heisman's approach is good but I'm not entirely convinced by velocity. I'm not sure the brain could internalise something as intuition that it has only seen fleetingly. At least for a beginner. This may be different for a more experienced player. There is a difference between recognising an idea you already understand or seeing something you already know applied differently, and learning it for the first time. Quantity and velocity works for tactics of course, but there is a difference between grinding out 100 knight forks and playing through 100 games that might have 10 knight forks. As you say, it is difficult to attribute a particular technique to improvement. Evidence is mainly anecdotal and people have preferences. It's easy to attribute success to an activity you enjoy but that doesn't mean there is a causal link. 😁
Hello!
I'm not quite 1000 yet, but I believe I will get there soon!
That being said, I almost always win my games by sheer material advantage.
I don't know openings by heart, I have no strategical notion, and often "won" games last longer than they should because I missed mate, or turn them into stalemate draws.
What are some good books to remedy this situation? You can look at my profile and see that I'm not a 100% begginner, but I really could improve my fundamentals...