tough time breaking into 1000 blitz

I haven't been playing nearly as long as you have, but I feel your pain. I'm only around 550 blitz and it seems like the people are insanely good and think way quicker than I do. Im sure you'll get there though. Keep plugging away and try to minimize mistakes.
"I'm just not thinking when I play"
++ Play 15|10 rapid instead of blitz. Think 40 seconds per move.
I just don't want my rapid to go down rn before I buff up my blitz. I got my rapid up to above 1300 and was really happy about that. Then I got my bullet to 700 which was like wow I can play bullet now.
In your life you have limited time for chess.
What do you value more: two 15|10 rapid games, five 5|5 blitz games, or fifty 1|0 bullet games?
For progress two 15|10 rapid games are better.

To most of my students, I give this advice (and it's almost all they need):
The biggest reason people struggle in lower-level chess is because of blunders. They make them in almost every game.
A mistake can instantly put you in a bad position, no matter how well you played earlier: if you had great opening knowledge, great positional skills, great endgame skills, whatever; a single mistake can change everything (you lose a piece or get checkmated).
So, how do you avoid blunders? Follow these two simple steps:
1. After your opponent moves, think if it's dangerous. Ask yourself, “What’s his idea?”
2. Before you make your move, think if it's safe. Ask yourself, “What attacking replies can he play?”
If you feel like getting to levels like 1600, 1800, or 2000 in chess is super hard, let's look at it in a different way. Those players you're facing make blunders in nearly every game they play. Beating them isn't so tough if you stop making big mistakes and start using their slip-ups to your advantage.
Again, it does not require you to become a chess nerd or spend all your time on chess. Just doing this one thing can boost your rating by a few hundred points right away.
Lastly, while avoiding blunders is crucial, I also share a few basic principles with my students. These principles help them figure out what to do in each part of the game - the opening, the middlegame, and the endgame. Understanding these simple principles is like having a map for your moves. When you use this knowledge along with being careful about blunders, you're not just getting better at defending. You're also learning a well-rounded approach to chess. Keep in mind, chess is not just about not making mistakes; it's about making smart and planned moves to outsmart your opponent.
Being a bit more specific, at this point I feel pretty aimless with the black pieces, just don't like anybof the "available" opening choices and the positions they lead to. Generally seems like the Berlín is the most solid but idk I'd like to have some idea of consistently generating strong attacks with the black pieces instead of always having to deal with uncomfortable positions
Do not worry about openings.
You do not win or lose because of the opening, but because of blunders and tactical errors.
Berlin is confrontational: it is the bishop's pair versus the better pawn structure.
Each time you change openings you will lose more, not less.
It takes time and losses to accumulate experience.