Dear @Engin.Taze,
It looks like your OpenFAST simulation is now running without fatal error–the warnings you are receiving now are not fatal and OpenFAST is completing normally.
Regarding the requested output channel warning, these HydroDyn output channel names were changed in OpenFAST v2.6 and the old names are no longer valid in newer versions. Please see the documentation here for the most up-to-date output channel names: https://openfast.readthedocs.io/en/main/_downloads/3f19498a5dc774461e022b671ff01ec6/OutListParameters.xlsx.
Regarding your parallelization question, a similar question was asked and answered here: Questions about Parallel Computing.
Best regards,