You are bound by DL's Contract of Carriage. http://www.delta.com/pdfs/contract_of_carriage.pdf

An excerpt from Rule 100:

• G) 1) Compliance with Terms and Conditions of Sale
  Tickets are valid for travel only when used in accordance with all terms and conditions of sale. Terms and conditions of sale include but are not limited to:
  A) The passenger's itinerary, as stated on the ticket or in the passenger's reservation
  record; ....

Another section of Rule 100:

• 4) Where a ticket is invalidated as the result of the passenger's non-compliance with
  any term or condition of sale, Delta has the right in its sole discretion to:
  A) Cancel any remaining portion of the passenger's itinerary,
  B) Confiscate unused flight coupons,
  C) Refuse to board the passenger or check the passenger's baggage, or
  D) Assess the passenger for the reasonable remaining value of the ticket, which shall be no less than the difference between the fare actually paid and the lowest fare applicable to the passenger's actual itinerary.

Rule 135 also provides that if you don't show up, DL can cancel all reservations on that ticket.

Rule 240 contains provisions that DL will accommodate you if you have a misconnection. But since your flights into and out of ATL on 12/10 are on different tickets, it would not be a misconnection if you don't get there in time for your ATL-BOS flight. Accordingly, you would be at DL's mercy, just the same as if you overslept and were late getting to the airport for your initial flight.

Will you be okay if you miss your ATL-BOS flight? Will DL take care of you? Probably. But I don't think anyone here will tell you that you will be "protected" if you miss it. Thus, no guarantees.

I like the answer that JS gave you.