I'm a little confused over what you are proposing, Phil. It would appear that you are trying to establish a continuous link from the ancient world right through to the advent of chanties in the 1830s. We're all fine with music being used aboard ships at various points in the histories of many cultures, but to try to link them all up would be a helluva task. Personally I would be surprised if these forms had not been used aboard ships when the need arose at various points in history.
There are surely many reasons for their coming and going over the course of time, war being a major factor, merchant shipping sunk and commissioned at an alarming rate, impressment, and I'm sure many others. Chanties were very cost-effective when men were in short supply, but in better times they would not be needed. Here's a for-instance. Chantying had a bit of a revival in the 1920s in the last of the tall ships as they were having one last big push to compete with steam and oil. (wind and man-power being less expensive).

I think we can all agree that the chanty as we know it was introduced by ex slaves, or in the OP's case African crew members.

I would prefer to reserve the term 'proto-chanty' for those actual chanties that were in existence prior to 1830 and were prototypes of actual chanties.

There isn't a mountain of evidence, but what there is is found in the Gulf ports and the Georgia islands.

The word chanty as applied to a sea labour song didn't come into use until the middle of the 19th century. What they were called before that Gibb might have some idea.

Another little sidetrack. Whilst yes almost all of the chanty canon is in English they must have been sung in Dutch, German, Swedish, Norwegian, Russian in particular, and I don't mean those sung by chanty choirs in the last century which are just translations from the English. What would be worthwhile would be to flag up any of these that are known. (From the same era I would add c1830-60)