You are not using the right approach: there is an LL_VRAM_MB environment variable override for this purpose. Simply add it to your configuration file. For a system-wide setting (which is recommended in your case, since anyone using the viewer on your system will have the same issue), type in a terminal, as root:
It is normal that the viewer cannot detect the available VRAM in all cases (and in particular with iGPUs/APUs: they do not have any VRAM and use the CPU RAM as such instead...), since it relies on X11 logs (not available on a Wayland system) and/or on proprietary NVIDIA and AMD methods of getting the GPU VRAM amount. In your log, you can see:
Also see the cool_vl_viewer.conf file in the viewer installation directory for more options that you can set with environment variables.