Is Betty going to suffer through PPD? Did she actually go in to check on the baby when it started crying? I saw her hesitate in the hallway and then she just kept walking. Was she walking to the baby's room or past it?

I think she hesitated in the hall because she is exhausted and probably not sure of herself as a mother. So, yes, it does sound like PPD. Also Betty not being too mature. Betty isn't usually the most wise and nurturing mother.

Agreed. Her parenting style isn't ideal. There is a pattern to her approach. She often tells her kids (especially her daughter) to just "go watch television" when she doesn't want to deal with them. And she wasn't particularly excited to have a third child, either. I could see them integrating PPD into the story line somehow. I'm not a big fan of the Betty character (despite her seeming complexities) and I could see this new baby taking a further toll on the Draper marriage. Not sure how, though.

I expect (or perhaps I hope) that the marriage will be better, at least for a while.

Don seems to be doing more honest reflection on his behaviors toward Betty and their marriage.  His first priority has been to preserve his "secret". His focus has been WHO am I?  A fugitive  denying my  past and always ready to run.  To WHAT am I?   A husband and father that is just as concerned about the emotional well being of my family as I am about my success at my job and the financial comforts that I supply?
 
Perhaps Don has come to realize that if the Hobo left a mark on his gate today, it would be, as it was for his father, the mark of a dishonest man.  That would make him more like his father than he could ever tolerate.

Both of them have been living in emotional isolation, especially Betty, (so glad to see Francine back in hr life ).  The next Time Don delivers his famous "What do you want me to do?"  she needs to tell him, " talk to me,  listen to me, tell me who you are, tell me what you want"

To under stand that relationship from Betty' perspective, imagine all that you know about your wife or husband's life before you met,   all of the fun and sadness and triumphs and failures, and if you were not welcome to talk about things in your own past, that had an impact on you, good or bad.  That sharing creates a bond of understanding between people.

Good points there. I can't imagine any 9-10 year old marriage today where one spouse knows virtually nothing about the other's past.
Don to Adam: "My life moves in one direction--forward."