How many of the 56 signers had not completed what we consider now to be primary education and who were they?

If you mean that in terms of formally attending school through the 6th grade, probably none of them did. Although schools did exist most people were tutored at home and/or self taught. Even the college graduates among them would have received their primary education in that manner. Thomas Jefferson had tutors and then attended Willam and Mary College. John Adams was taught by his father before attending Harvard. Ben Franklin had one year at the famous Boston Latin school but was otherwise completely self taught. Most of the signers had not attended college but they were all very well educated men.Michael Montagne