How can I repeat each song in a playlist n times?
You may have found this answer or another one by now but a simple way to achieve this (as long as you don't want to use the shuffle function) is to manually create a playlist and add each song multiple times.

Example (.m3u playlist in same directory as music):

#EXTM3U
a.mp3
a.mp3
a.mp3
a.mp3
b.mp3
b.mp3
b.mp3
b.mp3
c.mp3
c.mp3
c.mp3
c.mp3