Deal with the consequences.
I do that when I'm bored, but I'm not stupid enough to save after the fact the towns are far too empty without the npcs. Just one missing character, and it immediately feels too quiet for me.
Named NPC's never respawn.
Once they are dead, they are dead, nothing you can do, sorry.
Its always interesting to start a new character and take him down a different path, experience different sides of the game.
Whether you think the story of your current character is over or not is up to you. You could also incorporate the events that led to the death of Riverwood in your roleplay.
If you like the character... do you need to restart anew? What about an earlier save?
..... no words, a werewolf has more control than you man
This is the reason why Bethesda make every NPC essential because people kill everyone in the game and complain there is no one left.
Yep. They are definitely going to make all named NPCs in the next game essential. "Duhhh, you mean the NPCs that I killed don't come back to life?"