My most recent conclusion is that most of the time it is not worth the time to sell stuff used. So either keep it or donate it. I do like the trade idea.
So I second the second bookshelf idea. It is ok to buy one. Also ok to tell your wife that's what you're going to do because you also live in your house.
This is correct. I remember getting patterns from a magazine.
Also, there are flashes on-screen that could guide you if you are quick enough.
ETA: Just watched a walkthrough of this game. I've never seen the ending before today! I'm certain horny teenager me would have just loved to see the princess's huge nipples.