I just Beat The GMAT!

Very nice improvement - congratulations! I know you're still hoping to get better, but take a moment to savor the victory you've achieved so far.

Ideally, you want to finish the section with maybe 2 minutes to spare. That extra 5 minutes could've been used on some questions to check your work or just work more methodically and maybe avoid a few careless mistakes. (We're always going to make some careless mistakes, but it's nice to minimize them as much as we can.)

For RC, what have you been using to prepare so far? Here are some additional ideas to try: https://www.beatthegmat.com/verbal-strategy-t14035.html

For quant, I suggest looking around here (BTG) to see what others recommend for advanced quant study materials. Obviously, I have a conflict of interest when making recommendations of this kind... I will mention, though, that my company has two workshops for advanced quant concepts (one's actually called Advanced Quant, and the other is Advanced Data Sufficiency). You can look at our web site for more details (look at the One Day Workshops area).

One more thing re: timing. You're always going to see a few questions that are too hard for you to do in the given amount of time - no matter how good you get. Remember that, sometimes, your best response is to say, "Too good. I can't do this in the given time. I'm going to guess and move on before I go over time and end up hurting myself on other questions later in this section."

Have you been using our book? Or, if not, what have you been using to learn how to tackle RC?

You definitely need to reduce the time taken on that read-through. Because of the length of time you state, I assume you're trying to understand the whole thing thoroughly. Do NOT do that. On your read-through, your task is to do two things:
(1) understand the MAIN points (overall point of the passage and the one main point for each paragraph)
(2) know the purpose of each paragraph and the kind of stuff it discusses

You should NOT be able to tell me much (if anything) about the detail in each paragraph after your first read-through, beyond where the detail is located (by paragraph). You should be able to tell me, "Oh yeah, paragraph 2 is where they talked about the collapse of black holes." And if I said, "okay, well what did they say about the collapse of black holes?" your response should be, "I have no idea. Give me a minute to read about it."

IF you get a question about the collapse of black holes, you know where to go. And if you DON'T get a question about the collapse of black holes, you won't have wasted your time learning about them.

(Note: about twice as many questions are written for each passage as are given to one person. So there WILL be stuff in the passage about which you are never asked.)

And this "only go for the high-level outline on the first read-through" technique is about more than just saving time. You will understand the main points much better if you don't get sucked into all that ridiculous detail.

(Note #2: this isn't how you should actual try to read and comprehend stuff in the b-school or the rest of the real world. Unless your boss ever tells you that you have 3 minutes to read something and tell her the outline only and then you'll have some detailed questions but you can treat it like an open-book test at that point. Uh... that's not what "reading comprehension" is about in the real world.)

Finally, remember that your diagramming (the notes you take as you read) is NOT about taking notes as you would have during school. You are not going to have a test on this material in 3 weeks. You're taking the test right now. Your notes are just to help you understand the overall outline and know where to go to find any details you may need. That's really it!

If you don't currently have a book or other resource that is teaching you how to tackle RC, you should get something - just ask around here and see what people have found helpful. Beyond the diagramming bit, there's a whole lot more that has to do with the different types of questions, the ways in which they tend to write tempting wrong answers, etc.