The OCSSW tools downloads page asks you to set the OCSSWROOT variable in your ~/.bashrc and source a file that sets a long list of environment variables including L2GEN_ANC (USER_L2GEN_ANC is optional). In your case:
export OCSSWROOT="$HOME/SeaDAS/ocssw"
source "$OCSSWROOT/OCSSW_bash.env"
This can have unintended side effects when the 3rd party tools in $OCSSWROOT/opt/bin differ from the ones provided by your linux distro. In particular, the configuration of some netcdf and hdf tools and proj may differ from linux distro versions. To avoid these conflicts, you can omit the source line and use the ocssw_runner script (this is what the SeaDAS GUI uses), e.g.:
$ OCSSWROOT/bin/ocssw_runner l2gen ...
If all this isn’t comfortable for you, it will be well worth a spending a few days wir links to command-line learning material.
The SNAP and SeaDAS GUI’s are very useful, but, as you have found, they don’t handle every use case smoothly. The command line (terminal) is very useful both for debugging problems and for batch processing.