And when I look at a blank page, I have no idea what to write, where to start.

Reposting myself, originally about procrastination but I find this strategy also useful in your situation:

For creative work my favorite strategy is a variation on what is sometimes called the vomit draft in screenwriting circles - intentionally create the laziest, worst version of what you are working on. The original vomit draft strategy is more about writing without stopping to revise or reflect or worry about the quality, but even that doesn't go far enough to penetrate my procrastination. So I make it my goal to create a bad version of whatever I'm working on. The laziest tropes in writing, the worst programming practices in technical work.

The principal is the same: anything that gets you moving gets you headed in the right direction, even though it may not seem like it at first. But sure enough, at some point I can't help myself and feel compelled to fix or improve my terrible work.

... 

My other primary strategy is kind of boring, just biking and exercise. Mentally I feel a lot different after a lot of cardio.

https://www.lesswrong.com/posts/2mH7v5doDqoCZSn6z/not-useless-advice-for-dealing-with-things-you-don-t-want-to?commentId=SuEEMuRoXTgfjkhhD

I honestly have no idea how to think clearly. Particularly from a blank slate, without prompting or real-time communication with another person, who can dig things out of me I cannot retrieve on my own, by reminding me of things with their questions.

The Rubber-Duck Technique: Get a rubber duck (or a figurine of some kind). When working through a problem, or trying to understand a new concept, explain it to the duck. As if it were a person.

Maybe the silent duck isn't enough. At least try it before moving on. But you can be the other person digging things out of yourself. You can play both roles; wear a different hat; a different mask. Mentally inhabit each role, as in method acting.

Ancient Greek philosophers sometimes wrote dialogs, with one standing in for the philosopher or teacher, and the other a fictional (or fictionalized) foil. These could make good posts in their own right, or at least the start for them.

Explaining things to real people, and to imagined ones, perhaps in the shoes of another imagined character, was very helpful for me in consolidating, organizing, and seeing the implications of my knowledge, internally. Daydream. In this way. Make it a habit.

Make up fictional characters. Write down their personalities and backstory. Maybe base them on people you know, if that's easier. Maybe they're based on a shallow single concept. Maybe they have complex inner lives. Have them talk to each other. Explain what they know.

I hesitate to suggest (because I don't know how safe this is), but consider tulpamancy: create an imaginary friend, capable of acting independently, out of a fragment of your own psyche, one, who by nature would draw the best out of you. Explain things to them. Have them explain things to you. I think, with your unusual mind, this might work well. Perhaps too well. You may not need to go this far. Be careful here.

That's enough for elicitation, but you also want it recorded. Perhaps, with better internal organization resulting from your self-dialogs, this will become easier. But techniques can help here too.

the fact that my best thinking is done in the middle of the night when I ought to be asleep

Keep a notebook by your bed. The electronic kind, if that's easier, but you must be able to keep it on standby and wake it up instantly to start typing, lest you forget things when waiting. The dead-tree kind might have lower latency, but newer computers, or tablets with physical keyboards can do this.

Speak your dialogs aloud and record the audio (or video too). Use dictation software to automatically write the initial draft. Then explain to the duck what is wrong with it. Or imagine one of your characters shredding it with (concrete, specific) criticism. Or ask your tulpa what's wrong with it. Fix that, and explain it again. Save versions as you go. Git may be overkill, but perhaps you already know it. Split your screen, or get a second monitor. Read your draft on one side, and note the key points in outline form on the right. Then flesh out the outline. Or just retype a better version using the draft as a reference. Whatever, etc.

With the elicitation taken care of, and the initial draft recording, what remains is simply to revise the writing, because quality writing is revised writing. It doesn't particularly matter how you do it, as long as you're iterating, and improving. At some point, when it's "good enough", you stop. How do you tell? Explain to the duck why it's good enough. If you can't, maybe it isn't. Inhabit another mask and read it with fresh eyes. What would your characters say? Ask the tulpa. Publish.

If you do get some good results out of talking with people, I'd recommend trying to talk to people about the topics you're interested in via some chat system and then go back and extract out useful/interesting bits that were discussed into a more durable journal. I'd have recommended IRC in the distant past, but nowadays it seems like Discord is the more modern version where this kind of conversation could be found. E.g. there's a slatestarcodex discord at https://discord.com/invite/RTKtdut

YMMV and I haven't personally tried this tactic :)

I understand your struggle. I dream of being able to coherently communicate my ideas in a structured, understandable and dare I say convincing manner. I succeed when I start with an idea, write it down and start adding notes, ideas and talking points. Then I start fleshing out the ideas, asking myself how can I explain that concept or idea, whilst building an evolving narrative. Usually what starts as a mess of notes evolves into something coherent when I put myself in the position of the reader, asking myself i) what am I trying to communicate; and ii) am I sure this is clear to the reader.

Reading your post, it’s obvious that you know how to communicate clearly. Half the battle is having the courage (and the time) to get started. Just do it! Hope that helps.

Hello MSRayne,

I do like the honesty in your question, and reading it does remind me a bit about myself. Even though what you are describing sounds like more than what I am naming here - parts of it sounds like you are a creative person, and an intelligent one. A part of being creative is having ideas spontaneously. I do not believe there is a one-size-fits all in this department. 
A violin-teacher and an ex-partner, both stayed up late. They noticed that they had ideas in bed or at night, and forgot them in the morning. So, they wrote them down then and there. I'm not sure that can work for you, but I'm still letting you know. 

The other part about intelligence, that it might seem like if you are intelligent you filter out more. I believe this is dependent on your personality-type which information is filtered out, but it might also be a sign that you are changing fast, and what you have learnt so far isn't working, so you are making room for something new. This assumption is also based loosely on the start of the other post you wrote, (I read a bit), as
growing up with narcissism is no joke, no fucking joke, and is not conducive to clear thought. The logic there would be that you are expecting too much of yourself, all the time, that even when you actually do think something clearly - it isn't clear enough, and it is drowned in emotional-reactionary noise. 

I can relate to returning to concepts, with a vague and undefined problem, over and over again. In my life it has shown to not be a sign of wasted energy, but simply a natural process of focusing on meta-problems. If you are doing the same, it might be a kind of important meaning/sense making background process. And so you are using some of your energy on trying to solve a complex problem, and you are doing it every day.