When does the form actually submit: the last question or the Ending page? And...

Hey @copyeditqueen. Welcome to the Typeform Community! 

1. Do the responses get submitted after the final question (and before the ending page), or does the respondent have to click the final Submit button on the ending page for it to fully submit the survey?

The responses will get submitted once the respondent clicks on the "Submit" button, in the last question of your form. The Ending page is shown after the submission :)

2. Also, I noticed that when I test and click Submit on the final page, it loops back to the first page of my survey. I’m worried that respondents will think their response didn’t go through since it brings them back to the beginning. Is there a way to force close the survey page after its completion, or would I have to redirect to another page to do that?

By default, your Ending screen has a button that will restart your typeform, but you can toggle this on and off, and also change the text/hyperlink of the button. 

Hope this helps! Let me know if you have further questions =)