technically yes, most constrained-platform ports (as I remember) do the same though (DOOMQL, the TI-84 version, the Excel one) since BSP is hard to fit into a limited VM. "DOOM-style" here is more about the genre than the rendering technique
This is a FreeType issue - it uses auto-hinter by default on Linux and doesn't run the TT bytecode. No fix from CSS side unfortunately. Works on Windows/macOS where DirectWrite/CoreText run the bytecode
Frame rate depends on the browser - Chrome gives around 30-60fps on my machine, but the bottleneck is actually Chrome deciding whether to re-run hinting at all (had to add axis jitter to force it). The TT bytecode itself executes fast, it's maybe a few thousand instructions per frame
The recursive FDEF thing is the worst part honestly. Every while loop is a function that calls itself, and FreeType kills you at ~64 deep. So you're constantly juggling how many columns vs how many ray steps you can afford