Btw there's a bug in the empty field before the lizardmen encounter, there's a section that you can pick up root, but it'll trigger the lizardmen fight even though you're not in the next section yet.
Speaking of lizardmen, from my experimentation with several saves. Seems like you really have to let Sheva's crew die here (if you chose to save Awati) to fully corrupt Evelyn. Kinda suck cuz the fight while challenging, is quite rewarding cuz of the lizardmen's swords drops, which are probably the best weapons in the game right now (poison + bleed = busted). Hopefully we get to the chance to fight them in the future to farm those swords.
Also, I did make a save before the circle fight. Will there be a reward for us in future updates if we manage to win without cheats? I'm preferring to the debuffs of course cuz I don't mind learning the defense skill from Evelyn.
The lizardmen bug has been reported and will be fixed in the next version.
As for Evelyn corruption, you need to make about three major corruption decisions to get Evelyn to turn, or two major corruption decisions and one minor corruption dialogue in camp. So, you can mix and match these how you want (Praying with Evelyn is the only action that lowers her corruption as well, so that might affect things too). Either way, you
can corrupt her while still fighting the lizardbois (For example, kill that surrendering slave, then fuck Sheva twice).
As for a reward for fighting Cnut honorably, probably not. Those are moreso there just to make the fight a bit easier, for certain character builds, as well as for role-play. The player gets away with that one. But hey, doing the right thing is its own reward, as they say!