Some customizing needed for form to post

1-Two title lines.
a) The first would follow a particular convention, i.e. John Jones on Sarah Smith (memoir author on memoir subject).
b) The second title could be more descriptive and personalized.
I don't see a way to have 2 titles. Am i missing something obvious? I could add another title field, but where would it show up on the published post?

There is only one title for a WordPress page or post. As such, you should only use one on your form. You can add a plain text line, capture your subtitle as a custom field, then in your page template, display the data which is stored in this custom field. The form will collect the data, but the template has to be forced to display the data you captured.

2- I want there to be an Author's Profile that includes a photograph of the author. The Post Photo field (AFAIK) appears to get blended in with the Post Body Content, and that's not quite where it should end up. It should end up in the Author's Profile which is a separate area.

This is not really related to the form which creates the post. It's more related to the logged in user. You have to register the user, then log the user in, and capture some details for their profile page. Then you have to create the author template which will display the author's details. It's not really related to the "create a post" form.

3- How is the Default Post Author determined? The default is the "logged-in author." How exactly does the author become logged in if I don't have the registration add on? Or is this information drawn from whatever they write in as Name when they fill out the form?

If you are not using the user registration add-on, then you need to register the user with built in WordPress functionality, allow visitors to register and create accounts, and give them the role of auther when they register. There is no way to create an author page for users who are not registered, and the name they fill in, in the form, will not be used to create any sort of account for them. It's just a name at that point.

3a- If I'm not using the registration addon (personal license) can authors go back and edit their pieces after publication?
Thanks.

There is no built in way for the submitter to go back and edit the content they submitted. That is true if you use the user registration add on or not.

This functionality falls outside the realm of what Gravity Forms can do. It's part of WordPress. The first 10 hits of this Google search bring up several explanations and ways to do it:
https://www.google.com/search?q=create+an+author+profile+page+wordpress

It's also possible your theme already includes an author template. I believe Genesis themes from StudioPress do.

The easiest way is to use the content template. Have you already created your form, and you are collecting all the data you want, but you just need to get the information displayed in the post? Please share the URL or the explanation of what you want to do specifically. Thank you.