The first error is one that has been discussed here: BIDS Validator error - [Code 55] JSON_SCHEMA_VALIDATION_ERROR (EffectiveEchoSpacing) . In short, it’s strange that is an error instead of just a warning, but can be fixed by adding a field to the JSON. If this is your only error with the BIDS files, then I would say it’s safe to run fmriprep and --skip-bids-validation
The second error is because subject_results is not a valid BIDS folder. You can just create an empty text file in your BIDS root directory, title it .bidsignore (with the leading dot!) and in that text file, put in subject_results/. That way, BIDS validator should ignore those files.
Hope this helps,
Steven