Hi Boston Hostel, 19 Stuart St, Boston, MA 02116

I don't know about directly near the convention center (probably not, it's a fairly newly built neighborhood and generally $$$) but there is a hostel downtown, not very far away in Chinatown

It only runs every half hour, and even with the current slow zone situation the ferry is slower than taking the Blue Line from Maverick to Aquarium. And that's not even factoring in the walk from Maverick Square to the dock.

Dave Epstein increased his forecast in the last hour actually — and he's my favorite local meteorologist, rarely misses

Salem is easier to get to by train than by car and unless you wanted to go to Winter Island or the Willows it's all pretty centrally located and doesn't need a car. As for the witch museums you mentioned, honestly those are tourist traps. At least the Witch Village certainly is, never done the other. Better spending your time strolling around Salem, looking at buildings, checking out the waterfront, or at the wonderful Peabody Essex Museum.

Walk if the weather is nice. If it's an option try getting on the train at Back Bay rather than South Station so you can ride the Orange Line straight there, otherwise I would prefer Green-> Red over Orange-> Red because of how long it can take for the orange line to show up (especially right now)

Rhubarb is definitely a traditional food here, but it's somewhat old fashioned. Many people don't have a rhubarb plant anymore and (at least in my family) the rhubarb pies were tied to people in the neighborhood growing rhubarb in the backyard.

There are two in Providence which are a lot closer than Provincetown. Mega-Plex and Club Body Center.