Here’s what I tend to do.
On my first draft of something significant, I don’t even worry about style—I concentrate on getting my actual content down on paper in some kind of sensible form. I don’t worry about the style because I have more than enough problems getting the content right.
In this first draft, I think about structure. What ONE thing am I trying to say? What are the 2-5 sub-points of that one thing? Do these sub-points have any sub-points? Make a tree structure, and if you can’t identify the trunk, go away until you can.
Then I go back and fix it. Because the content is now in roughly the right place, the second run-through is much easier. But normally that helpful first draft is full of areas where the logical flow can be improved, and the English can be tightened up. I think you’re missing this stage out entirely as when looking at your post I can find plenty to do. Here’s what five minutes of such attention does to your first para.
“When I was 12 I started an email correspondence with a cousin, and we joked and talked about the things going on in our lives. This went on for years. One day, several years in, I read through the archives. It saturated my mind with the details of my life back then. I had the surreal feeling of having traveled back in time—almost becoming again the person I was years ago, with all my old feelings, hopes and concerns.”
Keep at it—there’s plenty enough there for the polishing to be worthwhile.
It depends on your thought experiment—mathematics can be categorised as a form of thought experimentation, and it’s generally helpful.
Thought experiments show you the consequences of your starting axioms. If your axioms are vague, or slightly wrong in some way, you can end up with completely ridiculous conclusions. If you are in a position to recognise that the result is ridiculous, this can help. It can help you to understand what your ideas mean.
On the other hand, it sometimes still isn’t that helpful. For example, one might argue that an object can’t move whilst being in the place where it is. And an object can’t move whilst being in a place where it is not. Therefore an object can’t move at all. I can see the conclusion’s a little suspect, but working out why isn’t quite as easy. (The answer is infinitesimals / derivatives, we now know). But if the silly conclusion wasn’t about a subject where I could readily observe the actual behaviour, I might well accept the conclusion mistakenly.
Logic can distill all the error in a subtle mistake in your assumptions into a completely outrageous error at the end. Sometimes that property can be helpful, sometimes not.