Based on you being Marriott Gold and assuming you're hoping for upgrade chances, I'd probably stay with the Pinnacle.

Your use of taxis will be minimal if you're staying within the downtown core. Gastown is certainly walking distance. If anything, you might use the Skytrain ($2.50 one way) to get to Yaletown. Walking to English Bay will be a good hike but it sounds like you might have a car.

There is the Vancouver Art Gallery but no real museums. There are lots of good restos downtown but if you're looking for good asian restos, almost all of them (I say that because I'm sure someone will argue a resto or two) are outside of the downtown core. You've got to hit Richmond for the best Chinese restos - also doable on the Skytrain.

There are a couple of threads which talk about areas to see within Vancouver.