Can I use 1 (or 2) Disney Dining Plan table service credits to pay for my Fantasmic! dinner package?
Yes you can.
Yes! When we last used the DDP, we went to DHS and used 1TS credit for Mama Melrose’s for the Fantasmic. Based on current info I read on the official site, the three restaurants that offer the package (Hollywood Brown Derby, Mama Melrose’s or Hollywood & Vine) have a standard menu: non-alcoholic drink, entree and dessert (which is a sampler platter at HBD and MM).
a TS at MM will give you an app, entree, dessert and a drink.
We used 2 Disney Dining Plan table service credits per person at Hollywood Brown Derby for Fantasmic! Dinner Package. We were able to choose a drink (nonalcoholic, 
) any appetizer and any entree.
Hollywood and Vine is a buffet, you can eat as much as you want. They bring you your drinks. We were surprised at how much we all liked the food - and our dc love buffets so we always go back when we are on DDP. Note that they have character buffets for breakfast and lunch but no characters at dinner, unless there is another special event package going on.