Some people in the comments already said how they made their own or started work on different ESC's. I went through 5 iterations of the ESC after the post.
Unfortunately, I never got any hardware working reliably for pretty simple issues in the end, which is frustrating. Primarily, I could never get the buck boosters of the TI DVR830x to work reliably and there were issues with SPI voltage and behavor. This caused a failure of 8-9 out of 10 boards or sometimes an entire batch. To produce one batch here is expensive: 60% import costs, $40 shipping for 2 boxes (one boards, one components) and then there's the currency rate of R$3 to the $1. In the end, to produce one batch here feels like spending $1200 dollars if I were in the US.
Important: I'm not saying the booster of the chip doesn't work correct, but that it's probably something in the process of my production (the "pizza oven bake") or the design of the component values around it or routing of the board.
Anyway, moving on... I did huge amounts of research into field oriented control. I built a FOC simulator in python and there's some 150MB of documents related to FOC implementations, ranging from presentations of TI about the subject to application notes, research papers, etc, plus I include some remnants of the board designs. Obviously, no point including boards of failing hardware, so just the schematics...
From the image above, all blocks at the top are really easy. They're only conversions from 3-axis to 2-axis models using clarke/park transforms. The difficult part is the "angle and rpm estimator", which is where the magic really happens. Eroding all complexity... it's trying to figure out bemf magnitudes from the Ialpha and Ibeta currents (in a 2-axis view), so that over a couple of samples it can converge to an angle. Another piece of code then gets this angle estimate and figures out the rpm, which is fed back into the angle estimate, because the rpm doesn't change all that quick. All that's left is tuning and the correct L and R inputs for the motor you're using.
The repository is here, along with a README on where to find the stuff.
Disclaimer: No guarantees that any of this stuff actually works...