Discount at the stores, yes, but no discount for reservations.
Yes, make sure you bring the actual pass white you
Yes, we were there twice in the last month, received discounts as a pass holder both times.
Sign up for their email list and they will send you specials throughout the year. There are no actual "discounts" through Disney. Just "specials" seasonally.
Yes, depends on the time of year how much though.
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