If I turn on flatview, then double click on a folder, then go "back" flat view remains off. Is it possible to implement a true "back," a function that goes back to the same folder and view settings that I just had?
An alternative to using back button is to lock the tab, 2 out of the 3 different tab locks will open a new tab when you navigate to a folder. Right-click a tab or hold down alt and left-click a tab to set the lock. So, once locked a folder is opened in a new tab. Closing the tab should return you to the locked flat view tab. What you're asking for and what the lock does is pretty much the same thing except you're just clicking a different button (the back button versus tab close button).
You could turn off Preferences / Folders / Folder Behaviour / Cancel Flat View mode when folder is changed, which is what turns flat view off when changing folders.
Yonder's suggestion of using folder tabs is probably better, though.