1. It is hinted at when you meet them in EP3, and at the end if you choose Omid. She is sick in EP4 and Omid thinks from the baby and she replies she's fine rather aggressively because for some reason she doesn't want anyone else to know. She recognizes the baby picture thing by name which I forget, and she gets really upset over what happened to Anna on the tapes. Lee can ask her if she's feeling fine cause he notices the small signs as well. In EP5 the drinking in the attic scene shows it even more and Kenny picks up on it too by how hesitant she was to drink when she looks at her stomach. And finally at the end Lee already knows based on all the signs by now that when he says the "Walking for two" line she doesn't even deny it.
2. Nobody knows for now, but I think they aren't shown in the last scene because they can also be told to go to the coast for a boat, or to go to the Marsh house as well as the train so they can't be shown in one set spot. Who knows.
3. Just cause someone is still alive to redeem their-self doesn't mean they are immune until it happens, I like that he died anyway before he could it made it more realistic.
4. Duck was grabbed, Shawn wasn't. Duck had a higher chance of getting pulled back and bit than Shawn. Plus he's just a kid. Also nobody else is around to help him expect you, no one else gets there as fast as you do.
5. He does if you have Carley. Wish there was the chance to come clean another way if you had Doug.