1. There’s an option to do this which should be enabled by default in the Main config: “Resize uploaded pixels automatically?”. Is it not working properly or are you referring to something else? This is when users upload an image.
2. You can edit the Site Slogan in the Main Config to change your description. You can edit the /html/header.php file if you really want to add keywords meta but I believe they aren’t used by most search engines these days.
3. Possibly you have to switch the grid to use PNG in the Main Config change the “Output Grid Image(s) As” option and save your background image as a PNG.
4/5. Yes I believe it is.
6. I’m not sure what you mean, can you post a screenshot?