On the
DDP, you KNOW I'm a fan! I think your plan sounds solid. My only comment about Tutto is that it's expensive if paying OOP. Therefore, I think your plan to use the DDP for Tutto dinner will work out to save you money, and use your DDE discount at Le Cellier. If you ARE going to do the DDP, make sure to get the profiterolles for dessert at Tutto.
As far as DTD restaurants on the DDP, they usually add them later. Since DTD restaurants are not owned by Disney, they have to negotiate contracts and usually add them later. When we went to WDW in May on the DDP, we had several DTD options including Raglan Road, Earl of Sandwich, Wolfgang Puck, Planet Hollywood. It did NOT include Fulton's, which I know you like...but it DID include Raglan Road, which I also know you like. AND Earl of Sandwich was considered Counter Service.
Also, if you are thinking casual and whimsical at DHS, you might like 50s Prime Time. I thought the food was really good and comforting. Five star dining it IS NOT, but fun and casual it is for sure.
Hope that helps!?!