1> agree whole heartedly, an excellent game that is still progressing, another installment is due in the next few days.
2> he has stated previously that both of those messages are placeholders for additional content to be added later.
3> the conversation repeats at that point I believe because there is no more dialog with Doyle that is new in the basement at that point.
4> it is still a work in progress...
5> Guessing here... may be used in the future or may be there so that the merchant has a bit more depth that just a sleeping pill vending machine...
6> Those show in your journal, the red book on the table in your bedroom, you will pick it up and be able to look at it by selecting it when in inventory.