Can I use my walker

Yes, they even have wheel chairs if needed.

Absolutely.

Yes

I think so, yes

Yes - all public access points of the museum are ADA accessable. There are several elevators on site. Lightweight, portable gallery stools and wheelchairs are available to borrow from the front desk on a first-come, first-serve basis.

Theres like 4 elevation one even for people with walkers at the very front so yes it better and faster to use the elevation anyway