Hi hi! I'm glad you're enjoying the game! That first bug is completely new to me. I've replayed the game myself many times for testing and never had the card bug out like that. I also never got a bug report of that before. I will look into it and see if I can replicate it but that might have been a weird fluke.
Devotion points are supposed to be a type of way you act/react that gains favor with a specific character. In the case of where they show up, some devotion points will only show if you have prior ones. There's a ton of hidden paths that are placed throughout this game. I do my best to use the Star-Chart to notate where each point is and what requirement is needed to unlock them. If the pathways become too tedious, I can look into adding a mechanic to help out with that in the future. But, yes, if you choose one path for a devotion point it would need another save to go down the other ones. The game's design is built around choices you make affect your future which in some cases, choices made in Chapter 1 or 2, especially Choose Your Fates, can and will affect paths later in the game. Not all paths will be affected super dramatically; some are just a small dialogue change while others change whole scenes.
I hope that answered your questions! If not, please let me know and I can offer some more insight into the inner workings of the game. As for the devotion, I can try to work on making it a little less confusing. With so many points, it can be a bit tedious to keep track of everything.