Unless there's some mistake, I noticed a detail that may reveal a misconception about the timing of events.
The first appearance of O.swald's main waistcoat as Glen is the night before L.acie's execution, implying that it was bought for the party that precedes his succession.
However, at the actual ceremony where he drinks the blood and becomes the next Glen, he is wearing his old waistcoat and then during L.acie's execution, he's wearing the new one. Either that's a mistake (after all, I thought they said it happened together but maybe I misunderstood) or they are different days.
Resting after making a contract instead of immediately using the chain makes sense since it's supposed to be hard on the body.
This would make the order of events: L.acie tells Jack to come back in a week -> the next day (she's wearing different clothes), L.acie and O.swald talk in the tower "Why did you lie to Jack?" "I will be lonely without you" -> O.swald becomes Glen -> L.acie and O.swald talk in the tower "The Core is lonely" -> on the fifth day, she's executed.
If this is true, it really does make O.swald's decision worse because he had the authority and opportunity to save her longer than if one event immediately followed the other. Tbh this might be a misconception that only I had and everyone else knew this lol.