From what I can gather, the saying you've asked about is more likely a traditional saying than an attributable Hadith. Of course, this doesn't mean it's not good advice; just not a validated saying from Prophet Muhammad saws.
Kanga, I am a read/write kind of learner, and I recommend learning the letters one by one, then how they connect, and going from there. Still now, in order for me to learn a new Surah, I have to sit down and copy it in Arabic in order to remember it correctly. My Arabic is not good, but I did learn the basics of reading and writing when I was in Peace Corps training. I am terribly rusty and need to make time. Also, when you learn these letters, you will learn and internalize the concept of Arabic roots, which opens your mind to more intuitively understand and connect meanings of words. I am certain you can do it. One letter at a time, and give yourself a long learning curve. You're a busy mama, and working too. May Allah make it easy for you.
On BC, I have been using an IUD since dd was born. At the time, I would say it was a unilateral decision...I think dh wanted bc in theory, but is not interested enough in the subject to have a real opinion. At this point, I would happily remove and try again, but dh insists that we're good, no more...so I'm keeping it. I also accept that if Allah wills, there will be more, and no bc can stop a power like that. And, we know it happens from time to time. What I like about my IUD is that it doesn't interfere with my systemic hormones, it vastly reduces bleeding (I didn't miss a day of Ramadan this year), and I only need to update every 5 years. What I don't like is that, if I do want to stop, I need an office visit. But maybe that is a good thing.
My dh travels extensively and is home sometimes for a week, sometimes more, and then is gone sometimes for weeks (he is on the road right now). I don't think charting or any sort of "being careful" would be feasible in our situation...at the risk of TMI.
So we're doing what seems to work, we are sincere in our intention, we are trying to guard ourselves and each other, and may Allah forgive us if we are in error.