I had previously mentioned Johnston's book, Connecticut Men in the War of the Revolution. I managed to download a Kindle version of it and went to the index of the book. Unfortunately, there is no Aaron Preston in the Index.
Perhaps the Ancestry Microfilm has been indexed in some other service, such as Fold3. I tried one hint from the AGBI, that Aaron is in Vol 12:173 of the microfilm. Well, the 173 is not a page number where you can readily see the name Aaron Preston. I also do not have the patience to read through it sequentially.
Regarding the death in "Carolina" in 1780. One, if that means Puerto Rico, is that he was a seaman on a ship who died of an illness. His marriage record says he was "of Norwich", and Norwich is close enough to the ocean that he could have worked as a seaman.
The other theory is that Carolina refers to the states of North or South Carolina. If he had been a soldier in the Continental Army under Horatio Gates, there were numerous battles in 1780, where he could have died in battle.
I hope this helps somewhat.