Questions around discrepancies in Redshift Copy Command

Hello community. We are observing a few issues in the Copy command from S3 to Redshift and need your advice. PS: We're using Airflow for Orchestration and use the S3ToRedshiftOperator for the copy command.

1. If there's an blank string in the tsv file stored in S3, copy command to Redshift writes it as NULL.
2. If there's a value as N/A in the tsv file stored in S3, copy command to Redshift writes it as Empty string.
3. If we have a value like phone number as a varchar in redshift, copy command is automatically appending a .0 to it.

Any advice would be appreciated. We're looking for the solution as to how can we remediate this. Thanks in advance!