Your CUDA graph in that picture says 89% and you are using 6GB of GPU RAM.
It definitely is using the GPU, the other graphs are apparently showing low figures because you are not doing 3D stuff.
If you need it to go faster now then you will likely need a better GPU.
Turned out the error is in the blacked-out path: One of the folders contains special characters in its name. And although spaces and hyphens are generally not a problem, it's a different story for non-ASCII characters like German umlauts. Apparently, PyCharm can handle them - but not venv.
This is not possible atm. Icons are cached for performance reasons. However you could create a file for each color using the RGB code in the name. This would bloat the cache but since you use /tmp this should not be much of an issue.