Regarding the Dothraki charge... that's what they do. It may not have been part of the plan, but when they all got flaming swords, they couldn't help themselves. They are not a terribly disciplined lot.
My belief is the NK had to personally off Bran like he did the previous three eyed raven. I wish the NK motives would have been explained and still hope that will happen.
The good guys are going to need time for themselves and their dragons to heal. I think there are still alliances to form. There are still a lot of people left in the far south.
I find this map helpful in following the action:
http://quartermaester.info/
The map puts the Umbers about six hundred miles from Winterfell, so the dead made great time. Helps if you don't need to stop for any reason.
Sam and Jon are the last of the Night's Watch. There is no need for the NW or the wall any longer.