if im using the Blackadam/shazam! duo, could i split them into the 140 pt shazam and another duo of black/adam shazam but using the black adam 140 pt? or can i use the duo 280 pt version and split them into 140pt shazam and 100 pt black adam from superman

Their name is Shazam! and Black Adam, so they do not meet the qualifications needed to Split.

As of now the 140 version of the figure is still named "Shazam! and Black Adam" as that's the name on the base and there's nothing that says "when you play it at 140 points the name is Shazam! instead." So you can't use the duo on the 140 point line as a single of that pair.