What was the source of the money Alden was pulling from the envelopes?
Who was it that he sent it to and why?
Why did Alden's wife (?) tear up the letter?
Van Alden has been intercepting Jimmy's mail. Jimmy was sending money to his wife and child. I'm not sure if he was using his address or Nucky's address as return but in any event Alden was stopping the transmission and opening the mail.
Van Alden sent the money to Jimmy's wife because Van Alden wanted to remove the temptation of using that money for his own personal gain.
Van Alden's wife tore up the letter because Van Alden told her in so many words that if she was infertile then that was God's will and she needed to learn to live with it. Apparently Van Alden doesn't really want a child with her and neither Van Alden nor his wife seem to consider the possibility that Van Alden might be shooting blanks. His wife views infertility as not only a curse but also evidently just really wants to have kids..