The local site is missing all the kfm_Directories tables?
Its the same install procedure and there are no errors while installing locally.
The kfm tables are only created when you use the image upload feature in the HTMLEditor, they are not created after running the installer.
In regard to making modification to your site. The Best way would be to run PowerCMS locally and Remotley, so all the paths are correct in your locat server and remote server. Once you have done that, set you your site that your testing server is pointing to your remote server. this way you can work locally and test your update and then uploaded to your remote server.
As far as updating the files, you only need to upload the current file you are working with and the Folder of the extension. For example, if you are working on eCart on the confirm.php page, you can just upload the confirm.php and the WA_eCart folder.
Let me know if you still have any other questions.