Getting the Nauxus Romance without Casualties is sadly impossible. You only got the choice between Sacrificing the Liazrd Spy or three other people.
Another Version of a good Ending if you want to save EVERYONE: "THANES ROUTE / No Casualties Ending".
Act1: Meet Nauxus in the Swamp ASAP and agree to save the Spy. Then go to the Bull village and meet Thane and Axel. Save the Spy. Suspicion: Nauxus 0 ; Axel 2
Act2: Help Thane. After you got the Fear Potion, take the Quest from Selye. (not Axel!). Sus: Nauxus 2 ; Axel 3
Act3: Listen to both chieftains demand but help Thane instead. Sabotage both sides. Recommended : allow Thane to stay at the Tavern. Sus: Nauxus 4 ; Axel 5
Act4: Give the Fruits to the Bull Tribe. If Thane is living in the Tavern, Axel prepared a surprise-basket for Thane. On the next day GO IMMIDIATLY to the Bull Village to prevent the Execution of the threee LIzard Prisioners. Suspicion Final Score: Nauxus 4 ; Axel 3
Downside: Nauxus will be salty and refuse any romance. You won't get the Star Emblem. You will also miss a bunch of Extra Dialog with both leaders.
The Main Problem is Act 4: You must give the fruits to the bull tribe, otherwise Eyvind will not arrive at the bull village on time to stop the execution. You are not allowed to gain more than 5 sus on Axel between Act1-3. We also should not help Axel in Act3 because the bomb comes with colletaral damage killing 3 Lizard Warrior. And on Act2 we need to asssit Thane otherwise the Lizard Trio or Tomahawk and his brothers will die. And to get Axel help for Thanes Kitchen Quest: Axel's sus < Nauxus Sus.
Fazit: You need to sacrifice the romance with Nauxus to save everyone. Period. Otherwise Nauxus vs Axel SUS = 3:2 by killing the Lizard Spy before you meet Naxus is the best outcome with the least amount of casulties.