Restaurant would have regular diners, like the OP's current reservation and package diners in there at the same time.
OP will need to book a package and cancel the regular ADR in order to get the seating at the show.
The only difference at TH for eating purposes (because it's a buffet) is package diners pay a little more for their reserved seat.
The range would be because there is: breakfast, lunch or dinner - child or adult - and seasonal pricing. So they don't put specifics on website.
This restaurant has run all over the place price wise, character wise .... hard to keep up.
Extra charge: Yes, just like Fantasmic package, Candlelight Processional etc.
Based on what I have found for adults -
Breakfast: regular $32, package $37
Lunch: regular $40, package $49
Dinner: regular $44, package $49
Tax and Gratuity are NOT included, so not cheaper.
From Disney:
Tusker House Restaurant
- Breakfast: $37 for adults and $23 for children 9 years of age and younger (tax and gratuity not included)
- Lunch or Dinner: $49 for adults and $30 for children 9 years of age and younger (tax and gratuity not included)
- Includes all-you-care-to-enjoy buffet access
- Disney Dining Plan eligible
Please note that while Tusker House Restaurant is available for all meal periods with this dining package,
you must dine at this location no later than 2-and-a-half hours prior to your designated performance time.