Explaining the 6th fetter? What is exactly meant by "Material rebirth lust", and how is it properly abandoned?
The 6th fetter's meaning pretty straightforward: the craving for the fine-material (or form) existence/Rupa-Raga. The lower 5 fetters are lower because they're all related to our world, which is the sensuous world (Kama-Loka), while the 5 higher fetters are those that are tie to the 2 higher worlds above Kama-Loka: Rupa-Loka (form or fine-material world), and Arupa-Loka (or immaterial world) (see Planes of Existence and RupaRaga for further details).