Yaatri the JFK-SEA trip was an afterthought to the BOM-JFK plan, so booked it separately online. Outwards, I am doing JFK-CVG-SEA and here are the rules that apply to me as per Delta on Y:
For travel within or between the United States and Canada, U.S. Virgin Islands or Puerto Rico and all travel to Brazil: SkyMiles Medallion® Silver, Gold, Platinum and Diamond members, Million Milers, SkyTeam Elite and Elite Plus members, and Alaska Air MVP & MVP Gold Members traveling in Economy may check up to two bags up to 70 lbs (32 kg) each at no charge on Delta and Delta Connection operated flights.
The rules you have quoted are correct, although I had assumed that weight had dropped down to 50 lbs (it's 50 lbs for non medallions or non-Skyteam elite Plus). I can't remember exhausting my baggage allowance during the last 10 years. The most I carried was three bags on my last trip to India, wit total being under 100 lbs and none exceeding 40 lbs. You are all set with DL with no issues.
If we used up all our allowance (4 plats travelling in business class would be 12 suitcases) when travelling together as family, we would need a small truck to carry the luggage.