On parables Make use of stories or illustrations (even through words) more than you do mere explanations. Show, don't tell. You can still show through writing, and this is where your next step is. Recently, you've been focused on the technicalities of writing, such as grammar and punctuation. Those things are good to understand, but generally are less important than the story you tell. If you haven't told a story by the end of your writing for other people, then what have you done? You've thrown information at a brick wall, most of which won't stick. That is ineffective and fails to make meaningful and positive change in anyone's life. Take a tip from the greatest evangelist to ever live and emulate his uncanny ability to explain and expose through storytelling. Analyze the greatest tales and proverbs and figure out what makes them so simple yet memorable.
On fiction Focusing on storytelling rather than the technicality of writing might even mean that you should spend more time in the fictional world to expose yourself to more stories than you do currently. As of now, you restrict yourself to nonfiction reading because you think that fiction is simple entertainment and serves no real purpose. That is true for a lot of people and has been for many eras. If you follow the crowds too heavily in your consumption of media, you will fail. However, that doesn't mean that there isn't something to learn from these stories. What is it that keeps you excited? Are there common threads among the greatest fictional writers that make them great? Also, what drives people's hearts? Storytelling is about winning hearts and minds. As you look out into the world of modern media, you see that plenty of hearts and minds have been completely won over by what is effectively fiction. A superstar dies and an entire world underneath them is affected. They are fictional characters that have been created and that is why they are superstars. Figure out what it is that makes their characters so captivating. Figure out what makes the fiction so inescapable.
On memory You won't remember everything you see, read, or hear. There are plenty of studies for you to consult on whether you should be reading, watching, or hearing your educational material. You could become paranoid and try to figure out which is the absolute best before you decide on one way to learn, but that would be counterproductive. The best book is the one you are reading. If you're reading a book on audiobook, then that is the way you'll best learn. If that makes you more likely to receive the information, then what does it matter that you'll retain more of what you learn in books? You're not reading the physical copies! It's also a game of numbers: If you can process 40 pages of a book in a day via audiobook versus 10-15 on a paper copy, then you can get through the content quicker and look for the true gems. My number one piece of advice to you is that whenever you are reading, you must be focused. You can't afford to doze off or allow your mind to wander. That is for later, when your intentions are to allow your mind to wander rather than to learn.