Create if needed will use the existing table if one already exists with the same table name, otherwise it will create a new one. So you shouldn't have to worry about those settings. Are you reloading the data? If so, you might want to try truncating it. I personally like to import the settings from the existing table, so all the lengths and types come through correctly, but that's just me.

That depends if you want to insert new records into the table (below the existing records) or empty the table and insert all records again (truncate option).

As mentioned you should see the changes (additional column) after updating the feature type (Writers menu > Update Feature Types) if changes are made outside of FME and need to be introduced.