I got his Best End, just choose everything that you think will please him, like accepting to pray when offered (and choosing sussy answers like "pleasure" and "i loved it" and stuff like that). Near the end choose anything but "walk away" and then simply "obey", in short - just be horny and obedient, lol.
Please don't apologize, it's always nice to receive questions!
I would like to preface this response by saying that Cirrus' route is very steeped in this fake lunar religion, and it's only going to get more blasphemous/intense in the next chapters. If this makes you uncomfortable, that is completely okay and understandable ✨ it doesn't need to be everyone's cup of tea, and in that case we would recommend sticking with Keir or other future love interests.
As for getting the best end, I think we do need to tweak the variables a little (bug fixing time!), but for story and character reasons, MC will likely still need to pray in order to get the best ending. If it is of any comfort, the prayer does not necessarily mean that the MC is religious themselves 😊
Thank you for playing Obscura, we really appreciate you taking the time 🥰