Hi Jennifer!
Fulton's Crab House at Downtown Disney is an excellent choice to make great use of the value of your Disney Deluxe Dining Plan! It's brand new to the Dining Plan offerings at Downtown Disney and I'm looking forward to eating there myself, on the Deluxe Dining Plan, for my upcoming 40th Birthday!
You are correct in that this is a 'Signature' location at which 2 Table Service Credits per person are required. With that, on the Deluxe Dining Plan, each adult will have your choice of a non-alcoholic beverage, an appetizer, an entree of your choice including side dish & a dessert. I've just called the restaurant directly and spoken with the staff there to confirm the allowable items for both of our sake. Fulton's staff clarified that the 'Add Surf To Your Turf' items are
not included under the Dining Plan but they may be added by paying the listed price for the item.
That being said, it was also confirmed that there are no 'exceptions' as to which
single entree you may order from the menu . If adding the lobster to a less expensive entree is still no more expensive than the other, pricier entrees on the menu, I'd definitely recommend asking your server about it especially since this location is so new to the dining plan offering. It could be quite likely that this 'rule' is in place such that a $50+ meal cannot be ordered in conjunction with
another add-on under the dining plan... but your specific request sounds reasonable and an exception could very well be granted.
Often times, exceptions such as this are done at Manger's discretion
(speaking from personal experience on the Deluxe Dining Plan) so it certainly doesn't hurt to inquire!
I hope you're looking as forward to dining at Fulton's as I know I am.
Wishing you a Magical trip to Walt Disney World Jennifer!
Kirsten