no, do not use 2 connection files.
use 2 versions of the same connection file. To explain that better:
create the connect using the information for the remote server, then upload it.
in the Dreamweaver files panel, change the drop dowwn to connect to the remote server server, open the connections folder, and right click the connection file, select the Set Permissions option and clear the read permission to make it a write only file.
now change the drop down to connect to the local server, and go to the database tab, edit the connection to use the local connection information.
this will give you one version of the connection file with the remote information that is read only on the server, another version of the connection with the local info.
If Dreamweaver tries to upload the connection again, it will fail.
as for the error message, I would need a copy of the WA_eCart\eCart1_PHP.php file to tell what the cause of the problem is.