Here is a consolidated and tightened dictionary / affix entry for [-ng], integrating your points while removing redundancy and clarifying the linguistic function.
-ng
[-ng]
Linking suffix; phonemic linker / ligature
A phonemic linking suffix that connects a modifier, prefix, or descriptive element to the word it qualifies or completes. It functions as a ligature marking a grammatical relationship between two morphemes or phrases.
Primary functions
In many environments it functions similarly to the linker /a/, but -ng appears under specific phonological conditions, particularly when a preceding element ends in a vowel.
Examples
Modifier linkage
Axaki-ng kaata-as.
axaki-ng kaata-as
man-LNK tall-INTS
“The man is very tall.”
Here -ng links the noun axaki “man” with the descriptive phrase kaata-as “very tall.”
Morphological linkage
Ammong-sayod
amo-ng sayod
amo-LNK sayod
“having resemblance / similar in appearance”
Here -ng links the prefix amo- to the root sayod, forming a unified lexical expression.
Notes
If you wish, I can also help you create a clean FB linguistic poster explaining the Boie’nen linker system:
/a/ vs. /-ng/
with examples like
This would visually complement your BOL + Old Boie’nen Dictionary project very well.