I cannot make the Delaware-Virginia connection for you, but here is what I have on the Ack family in Delaware:

1768-1784 Kent County, Delaware Tax Assessments
frame 420, 1780, Little Creek Hundred
negro Ack

Kent County Tax Assessments 1785-?
frame 73, 1787, Little Creek Hundred:
Free Negroes:
Needham Ack
Emerson Ack

frame 108, Dover 1788
Free Negroes:
Needham Ack

frame 138, Little Creek Hundred, 1789,
Free Negroes:
Emerson's Ack

1800 census for Kent County, Dover Hundred, p.51
Ack Nedham 10 "other free"

Paul