My favorite gloss is "to long (for)". This has the advantage
of having morally neutral connotations, while still indicating
a relatively strong feeling. This meaning fits most of your
citations above fairly nicely. It clearly is awkward in Acts 20.33,
but still gets the meaning across:
I longed for no one [else]'s silver or gold or clothes.
The meaning is close to covet, but "long for" is probably more
immediately apprehensible to a contemporary English speaker than
"covet" is.
The Matt 5.28 passage then becomes something like (translating
PROS as "for the sake of")
.. that anyone looking at a woman for the sake of the longing ...
This suggests that the problem is allowing my looking to be
intentional enough for me to relish the resulting endorphins (one
teacher calls them "the tingles"), whether those endorphins
result from an explicitly sexual desire or from desires for
companionship, etc. Not every affair (so I've read and seen)
results initially from primarily sexual attraction.
And yes, I agree with the correspondent who observed that, given
the context, Jesus is referring to a relationship that if
developed sexually would be adulterous, and is not talking
about the natural attractions of single people toward each
other.
Regards,
Jim V.