1) Currently, the min and max Y range for the chunk spawner chest is limited to -64 ~ 128. I believe it would benefit the mod to extend the valid range below -64 and above 128. The vanilla build height is higher than Y 128, and being able to guarantee a midair chest spawn regardless of biome spawn (maybe eventually with its own mini sky island) would be a worthwhile challenge. Furthermore, datapacks and mods that raise the build height or lower the bedrock layer (like Infinity Cave) would be made compatible.

2) When use_bedrock_chest is set to false, a vanilla chest is used as the chunk spawner chest. I think it would be best to always use the bedrock chest regardless of whether the bedrock_chest_unlock_at_blocks_remaining functionality is in effect. This way, the player cannot accidentally break the chest and an unique visual identity is provided.