Seems like a very fun setting and I like the different Saints.Using the Blessing pool to add to the rolls as a way to add to rolls seems like a fun way to give players some control over what they deem important. Setting wise I think the world has a very clear feel that vibes with the art as well, leaving it feeling like an old school morality play that could create a lot of fun moments of religious horror.
I think I’d like to test the blessing pool using a d4 or d6 instead of allowing players to decide how many points to spend initially and add that die to the roll, marking that many as a result to make the use of blessings less targeted. Also maybe add a rule for going over 12 (or rolling more blessing than remain) to be too much success. Add a little bit of horror and fear in using points. It would also help avoid players sitting on points until the end of the session to make the build up at the end of the game suddenly becoming trivial as players dump the last of their points into rolls. Limited resource systems often lead to FOMO early on and make engaging with it early seem like ‘wasting’ a resource you might need later on.
Other than that I’d maybe change the last two boxes in the character sheets a lighter grey to indicate they are added only depending on the Saint you choose, and add a space on the sheet to indicate which saint you selected. I’d also change the Saint bonuses to be Miracles instead of Blessings as using the term to both refer to the pool of bonus to your die roll and the abilities from your saint was confusing.
Things I’d like to see eventually added would be: Maybe an event table for the GM as a d66 based on the rolls the players have made in the previous scene that could help guide the next scene and what the encounters are moving forward to help the GM move the expedition along. Perhaps some temptations in the forms of rolls that the players may make only if they use their blessing points as a tool for GMs to help break players out of FOMO, and maybe a GM mechanic of a Sacrifice for players to allow players to regain blessing points either through dark means, or noble selflessness. Limiting the pool to 12 every session for sure I think leaves players in a less interactive mode of resource management, but if the GM is able to refresh those pools but with consequences I think it might give more horror tools to the GM to make players confront their characters biases due to the domains of their Saints.
Over all it does seem like a solid framework to build more on.