Roger has gone full bohemian, and he's struggling with the realization that he is old enough for it to be completely ridiculous.
I think the woman on the plane, it may have just been a colloquialism. The doctor told her that "they" have a year. Like, left in "their" marriage. It's a slightly softer way to tell her that this bitch over here gunna die.
And apparently Don didn't tell Megan he got fired. With pay or without. He's ashamed, and just putting on a show of it. But he also avoided the opportunity to philander, and I think Freddy might be a way that he starts to confront his near-alcoholism as well (the fact that the widows husband died from "being thirsty" is relevant). In order to get to California and have a real shot with his marriage working, Don's gonna have to confront his pride. Its so obvious that even Don himself knows it. His patio door is broken. His colorful penthouse looks like a ruin. He's got nothing to be proud of right now.
I think Don will get a not-tragic ending. Maybe not a completely happy one. And I don't think he's gonna turn into hippy-pete. But he won't turn into Roger.