Only if your card is still good.

Benefits are paid to the legal heirs of the sailor, not the widow - if the widow's children not born of the seaman had been legally adopted, it would be different.

Since the widow's children aren't legal heirs of the Seaman (either by blood or legal decree), they aren't entitled to any settlements the widow received as part of her marriage to the Seaman.

Not always. It is proper to refer to Seaman Recruits (E-1), Seaman Apprentices (E-2) and Seaman (E-3) all as Seaman. However, there is also Fireman, Constructionman, etc. So if you are a Seaman, Seaman Apprentice, or Seaman Recruit, then yes, you can be referred to as Seaman.

Seaman Jacobs's birth name is Seaman Block Jacobs.

Robert Seaman was 72 when he married Nellie Bly.