The spreadsheet should be simple enough. All you need is a top row with all the headings for each item. The script will append a row of new data when submitted.
We seem to have exhausted all possible issues. Only thing I can suggest is that you simplify. Create a new AppInventor app that just submits and image and data (e.g. test with my aia project and use your script web app url). Does that work ?
Now you need to compare what you have just done (code/blocks/script) with what you have in your app, and find the difference. You may need to simplify your app in order to find it. (Logins/Screen switching etc.)
Do you mean to send more data up to the google sheet ? The method is all there in front of you. In your blocks, add another parameter and set the data, in your script add another parameter, and add the parameter to the append section.
Follow the workflow for an existing piece of data, e.g. latitude.