Looks like you had a fun game. I'd like to hear how you decided on what Dark Spawn to use. I presume you were using D8/D10 and just varying what would emerge from the portals? I think you were right to continue the game once the atrocity appeared.
I used the Dark Spawn arrival as written in the rules for game 1 and 2, but that seemed a bit too easy for the hunters. I varied things a bit for the last games.
Game 3
Turn 1 4 x d6 Dark spawn, Turn 2 2 x d8, Turn 3 2 x d8, Turn 4 2 x d8, Turn 5 2 x d8, Turn 6 2 x d10
Game 4
Turn 1 4 x d6 Dark spawn, Turn 2 2 x d8, Turn 3 2 x d8, Turn 4 4 x d8, Turn 5 2 x d10, Turn 6 4 x d10