Split RTF document with headings as item titles

Is there a way to import a single .doc/RTF document with headings (one level only) so that it gets broken into Scrivener items with headings as item names?

Alternatively, once the document is imported as a single Scrivener item, is there a way to automatically split it at lines containing a markup character (*** for instance)?

If not, how does one import a large doc/RTF files without loosing its structure?

I think what you want is Split with Selection as Title. This is from the manual ::

15.3.2 Contextual Menu for the Text Editor
The text view’s contextual menu contains many standard commands such as Cut, Copy,
Paste, Spelling and so forth, along with a number of commands specific to Scrivener. The
Scrivener-specific commands (the appearance of which will depend on the selection) are
listed below:
Text Editing Contextual Menu
Split at Selection Splits the current document into two documents at the selection point
(the current blinking cursor point, or the initiating edge of the selection, which will
be on the left by default, or on the right when using right-to-left languages).
Split with Selection as Title Splits the current document into two documents using the
current selected text as the title for the newly created document. The selection will
remain after splitting, making it easy to remove the redundant title text if necessary,
or style it like a header. For more details on splitting documents, read Managing
Documents with Split and Merge (subsection 15.3.3).

This is fine when you have only a few splits to make.
I’m talking about importing large, >100K documents with > 50 headings and sub-headings.
You don’t want to split them one by one by hand.