Hi!
1; Myth resolution
I used the Forest, The Goblin, The Plague, The Wyvern, The Underworld, and The River myths in the campaign. I never really find myself in a bad spot. I cheated with the last omen of the River a little bit. The new lake was not born on the hex where the team was standing, but on a neighbouring hex what they saw from a ventige point (They used the portal cloak from one of the Underworld omen to "teleport" into the holding before it was washed away, so they could save 2/3 of the people.)
2; Group motivation
I think if there is a game where you do not have to worry about group coherence this is that game. They are knights, united by their knightly oaths and dreams of the City. In my campaign the knights were sent to a mission by the Dreaming Seer to find the Amber Knight. All came from a different realm, they met on the road, introduced themselves as knights should do, stated their cause and when they find out that they share the same quest, they joined forces.
3; Stat imbalance
Perhaps we come from different gaming culture, but I do not care about "game balance". I think in story and world logic and not in game logic. There was one knight who rolled really good stats (lowest stat was 14 I guess), one with fairly decent stats and one with horrible stats. I didnt meet any issue at all. Honestly I cannot come up with any theoritical situation where I would need game or stat balance. The level of the stats helped the players to imagine their characters. The one with the low stats were the Willow Knight, the player decided to justify the horrible stats by that his character is almost a kid.
4; Omen frequency
I used the rules stated in the book, during travel at the end of each Phase we rolled a d6 and based on the result I introduced an omen, a landmark or - if it was all clear - a little bit more detailed description of the environment. It worked out just fine.
To be quite honest, although I borrowed the basic premise from the author, I didn't use the game as described in the book. There was a "main quest", "find the Amber Knight". This was the reason the party even went to the realm in the first place, and I used the Amber Knight to "tie" the myths together. The whole campaign had an overarching storyline, a family drama between the ruling Chain Knight, his long believed dead wife and his even longer believed dead son (The Amber Knight). I invented an artifact that the knight used to open the door to the afterlife (The Underworld), these machinations upset the balance of nature (The Forest, The River, The Plague) and it was the Goblin from whom he had previously lured this long lost artifact.
The mythos was strung together on a pretty deep and detailed lore, but it's important to note that I wasn't prepared for this at all. I had no idea at the beginning who the Amber Knight was or why he had to be found. I had no idea about the Black Codex, the family drama in the Chain Knight's past. I just ran myths and threw in info via NPCs as ideas came. THE only thing I was very careful about was that information that was already "canon" was not contradicted later. So sometimes I had to sit down between two sessions to think hard, but the story somehow wrote itself, miraculously. I call this technique Schrödinger's Lore :D. Throw in interesting stuff, basically clues on the spot, then later figure out how does it make sense :D It sounds stupid but I swear it works! :D