> in that I really dislike following someone else's structure/rules and don't like being controlled, micromanaged, watched.
Stop. Unless you actively hate the situation you're in, e.g. hate your job, your work, your boss, whatever (in which case you need to get out), take a step back and evaluate whether the structures and rules are really intrinsically bad. If not, stop fighting them, take comfort in them. Obviously it makes you calm and settled once you just accept a particular rule framework.
> I have a strong aversion to discipline, and can never get any productivity/organizational methods to work.
I don't know you, but are you brushing your teeth every day (even just once, say, in the evening)? Do you feel odd if you skip it? If so, you obviously formed an habit there. Habit forming is hard, but it works. Make it a tiny thing at first, i.e. "sort emails every morning" or "check your todo list every morning". Not more.
> I work very slowly, both at home and at work. It takes me longer to do the same tasks compared to others at work, and at home I can only accomplish just a few mundane things that take up most of my day.
At work: Let's put that down as a strength. You are good for tasks that require an extreme level of detail. Find work accordingly. At home, especially with this:
> and/or I'm thinking about stuff.
... I found that my productivity in mundane household work improved by 9000% by listening to podcasts or audiobooks that I enjoy (or watching videos if the task allows). No, not a work-related, self-help, or "weight of the world" investigative podcast. Something fun. Something you really care about, but in a lighthearted hobby way. Like videogames or vintage cars, whatever floats your boat. (Maybe boats?)
I can get so engulfed in what I'm listening to that I'm often actively looking for other mundane, mindless household work so that I can continue listening.
> I just want to sit down and read my books and write my essays but I can't
Well obviously you don't, and also:
> 2) when I get some free time I get anxious about having to use this time wisely and productively and end up not doing anything.
Stop. This is bullshit. You are wrong.
Free time is for staying in bed, binge watching a stupid TV shows, falling back asleep, and waking up at ungodly times. For sitting on the floor with coffee and do nothing.
And then at some point, when your mind and body had enough for that, you will feel the ache to be productive. To continue reading that science text book, to write that essay. It will feel actively boring and bad to consume instead.
Until your mind and body are exhausted again and you start consuming again. Playing videogames, wondering how you could ever be motivated to write an essay. And the cycle continues.
"You have to be productive" in your free time is one of the most infuriating bullshit mindsets I've ever encountered, and it seems to grow. If I felt that I had to be productive during downtime, I'd never be! What an awfully exhausting thought.