Thank you for the details, OP, which I will reproduce.
Wikipedia defines Ebonics as ” the language of all people descended from enslaved Black Africans, particularly in West Africa, the Caribbean, and North America”. That includes AAVE, Bozal and any number of creoles, be they derived from Indo-European languages or not. Since the peculiarities of African-American English have had (more dull, admittedly) names before, this understanding of the word seems to make more sense than the one I encounter, “BAE if you want to raise a stink about it”.
The definition is news to be, I assumed Ebonics was only AAVE (African-American Vernacular English), and was not extended to creoles. That’s certainly how the term originated.
Even under that definition, that would not make Ebonics a Sprachbund, just a cover term for a number of genetically (?) related lects. For there to be a Sprachbund, there would have to be ongoing contact and structural coalescence between them. The opposite is the case, as Shuochen points out.