SuStel:

Why are you trying to come up with the one true way to say these things?

I'm trying to shed bad habits which have accumulated over time, such
as using {-nIS} to express "must" regardless if it is the right thing
to do.

Remember that the discussion showed no perfect resolution to the issue of need/must for -nIS. If you do want to avoid using -nIS to mean must, then simply do so, and use whatever other tools are appropriate for a given sentence. There is no single tool that is best.

-- 
SuStel
http://trimboli.name