Nitemare

You can Uber anywhere. You can also take MBTA Commuter Rail or a Ferry boat from Boston to Salem. You can walk as little or as much as you want in Salem. Which museum are you referring to? Salem has more than one! The PEM is the best one, IMHO

You climb down 2 or 3 steps and climb up 2 or 3 steps. They will help with luggage if you need assistance.

Aim to arrive 4-5 hours before sailing. There aren't going to be any traffic problems that tie you up that long. And if something like that DID happen, there will be a ton of people missing the ship, they won't leave.

Chelsea hotels are often cheaper and many have airport shuttles. Not many attractions right there, but you are close to public transit

Which terminal matters. New Jersey would be much easier than Brooklyn

There's no guarantee that they won't change, but I'd count on it staying Brooklyn. The good news is, it's pretty easy to get to either port from anywhere in Brooklyn or Manhattan. Subways, ferries, uber/taxi all run all the time

There are a couple helicopter tour companies. I'm sure one of them can arrange something for you for the right price

I wouldn't be surprised if fellow cruisers had booked them all in advance. They cancel when it's windy

Taxi or Uber is likely going to be much cheaper than the Princess transfers. Especially if you have more than 2 passengers. They will charge you $X * 4 for their bus, the Uber/cab costs the same for 1, 2, 3, or 4 people.

Heimey has some great RIB boat excursions you should be able to book directly. They cancel them in bad weather -- we had wind on our day there a few years back and all tours were canceled (as was our ferry back to the mainland), but we were there in September and it gets windy in Iceland around that time. We had a car and explored the island, loved it, but the RIB boat would have been a blast

Hundreds of reviews here: https://www.show-score.com/broadway-shows/hadestown-broadway You will get much more info from a site like that then just a few replies here. IE: @George C liked it. I didn't like it. My wife thought it was ok. But Show Score gives you more info, like things to compare it to. Casts change, too, so my experience may be quite different than yours. For instance, we LOVED Hamilton almost every time we saw it. But one time we attended, the actor playing Hamilton didn't have the same charisma, so we didn't think it was as good.

Me, I'd walk it. Of course if you have too much luggage that's out, but your best alternative is a taxi. You could check www.straeto.is which is the public bus service to see if they cover your route. You'd need their app or cash to pay, I believe

Jack is right. July has daylight for 24 hours. Anything erupting now will likely be done before July. And another one may or may not be going off during your visit. I wouldn't book anything volcano related more than a week ahead of time.

Usually runs $125-$150, per reports on TripAdvisor. No tipping in Iceland, you pay the metered fare

If we are talking Reykjavik, there are taxis, but the Flybus is usually a much better price, unless you are more than 3 people