FWIW Shareful ( Shareful on the Mac App Store ) allows you to do all of these:
Byword and Ulysses automatically convert the exported rtf data to Markdown, though Drafts does not.
Also, a lot of what’s needed to do the other tasks you describe is already there & accessible though AS - run this in Script Editor:
tell application "Notes"
set n to selection
properties of item 1 of n
end tell
See also Applescript and 'notes': Open note in new window - Stack Overflow