It depends on your recovery requirements. Synchronous commits to the secondary before committing on the primary so depending on network speed between the primary and secondary that can add an...

If you are making changes in production you should have in place a change management process which generally prohibits ad hoc changes to production systems. One should have at the...

Oracle SQL Developer Data Modeler is free and very nice.

Please post create table script and insert script with sample data, you've provided what you've tried already, and desired result.

Try creating a BCP format file for the import.
https://docs.microsoft.com/en-us/sql/relational-databases/import-export/create-a-format-file-sql-server?view=sql-server-2017

I agree with Andy. Your query would benefit greatly from a covering NCI.

That depends on what the scripts are doing. If you are altering an object I would say serializable, however, for DDL, your script will wait for a current query to...

Have you an SPN for the server name your using in your connection string? Is SQL Server running under a domain account?

If you have to do in place, do you have the down time to backup all the databases, script out logins (with SIDs) and jobs, all to a network share,...

What Oracle providers are installed on the SQL Server? What version of Oracle is your Oracle Server running. Sometimes a data type is being used and is unsupported by an...

Have you tried Oracle Developer Data Modeler?

I believe they will. Try it on a smaller heap table.

You make the login and password parameters and set them in the job.