Yes.
Yes.
Right after flashing Android 13 (62.2.A.0.525) and then restoring SFOS, I disabled the brightness fix service. It was some four days ago and since then I haven’t seen the color banding issue or the yellowish tint a single time. So I guess it is safe to assume that it is gone. Together with the echo issue which is also absent.
I’d recommend you to do it the way I did it, i.e. use dd (in recovery mode) to backup rootfs and home (/dev/sda79 partition), flash Android 13 using EMMA, and then simply restore SFOS from backup using dd. This way you can change the underlying Android version and quickly and easily get back to the exact same system you’ve had…
Please see Full dd backup of rootfs and /home as flashable images - #26 by wetab73