When you say your reading speed is fine for passages, give me an idea of the actual timing. How long does it take for you to read a shorter passage vs. a longer passage? (I'm talking about the initial read-through, before you address questions.)
If you are struggling with finding the answers to specific questions (both inference and straight what / why detail questions), then you are not paying enough attention to the structure of the information in the passage.
The passage as a whole has a "Big Point" - what's the one-sentence reason why the author wrote the passage?
Each paragraph also has a "main idea" - why did the author write this paragraph? (Note: for shorter passages, some paragraphs may have two main ideas) What kind of information does this paragraph contain?
Notice that I said "what
kind of info" not "what info." I don't want to write down all of the details, or even read them very carefully at the beginning - that takes too long. But if I notice that the entire passage's Big Point is that artificial fertilizers are harming butterflies and we should use organic fertilizers instead, then I also want to notice that paragraph 1 tells me the Point and gives me some background, while paragraph two details how the artificial fertilizers harm the butterflies and paragraph 3 discusses alternative fertilizers that could be used and also mentions that the author thinks environmental laws should be passed to force the farmers to use these alternative fertilizers.
How, specifically, do the fertilizers harm the butterflies? I don't know, but I can find out in paragraph 2, so that's where I'll go look if I get a question about that. What's the author's tone? Oh, that one I know without going to look - the author is using a persuasive writing style to try to get the audience to agree with him / her. Why does the author discuss the Environmental Protection Agency's role in the regulation of pesticides? I don't know, but paragraph 3 talked about environmental stuff so let me go look over there. Etc.
When you are tempted to get too into the details on your initial read-through, remember that there are something like 6-8 questions written for each passage, but you'll only be given 3-4 of them. In other words, there are details in the passage about which you will NOT be questioned. So why learn the material up front?
If there are certain topics that trouble you, try to figure out why. Politics and civil rights - are you bored to tears and, because you're not interested, you lose focus? Do you try to bring in too much outside knowledge and overthink things and that gets you into trouble? When you lack knowledge about the topic, does that psych you out because you think, "I don't know anything about this!"? (Remember that all of the information you need to answer questions IS in front of you somewhere - RC questions do not require outside knowledge.)
As much as possible, try to study from the OG for this stuff - the language is so very particular that you need to get a feel for the real thing. Even though we try our best to mimic that, it's still not exactly like the real thing. You say you're done with OG11 but you're not really done with it if your score isn't where you want it to be. You haven't learned everything you could learn from that material. Don't just keep doing lots of new problems. Take the time to learn everything you can from official problems - everything from passage structure to how questions are worded to how right AND wrong answer choices are worded, etc.
For SC, if you really know the rules but still can't figure out how to apply them to GMAT-type sentences, here you might need some outside help. From your description here, I assume you have been studying this and do know the basics but you feel like you are hitting a wall and just don't know where to go. That is often a sign that you need some outside help - whether from a tutor or from a friend who does actually understand how to apply those rules (and is able to explain to you in a way that you understand).
And don't use 1000 SC. There are tons of errors and bad questions throughout there. Go back to OG again.
