My questions:
1) the ability to go from park to park on the same day basically means it's a park hopper. correct?
Yes, that is correct
2) What is the difference (if any) from Memory Maker & Disney Photopass downloads?
Same thing. Photopass was the original name, now called Memory Maker
3) Typically, are the "special offers" at Disney Resort hotels similar to the 10%, 15%, 20-30% structure that they do. I realize that who knows what Disney will do in the future, but historically what has it been?
AP discounts often come out a few days before the 'public', but generally the same discounts
4) What about discounts on dining & merchandise? Again, I know there are no guarantees on what Disney will do, just what have people had in the past?
Discounts, and other benefits....
http://allears.net/pl/apass.htm#bene2016