If you have tab debug in DragonAPI enabled - I think it's on by default - you can hold tab on the ritual altar to see its NBT tags; one of the tags should read something like "multi: xb". If x is 1, the multiblock is correct, otherwise it isn't. Keep in mind that the crappy repeaters only have a range of 16 blocks (if available, a bibliocraft measuring tape set to absolute is really handy here), and just like proper repeaters are very sensitive about unobstructed LOS.
As for the other thing, the block of code here (l221) is presumably to reduce the chance of young entities from being killed before they can react - like, say, the player immediately after logging in. The block of code here (l235) is because Reika really wants to make sure there's no way to avoid the damage... however, if amt happens to be less than originalAmt at this point, like, say if the entity is sufficiently young, it will indeed trigger the anti-anti-damage code and deal the full damage anyway. Good catch.
As for the other thing, the block of code here (l221) is presumably to reduce the chance of young entities from being killed before they can react - like, say, the player immediately after logging in. The block of code here (l235) is because Reika really wants to make sure there's no way to avoid the damage... however, if amt happens to be less than originalAmt at this point, like, say if the entity is sufficiently young, it will indeed trigger the anti-anti-damage code and deal the full damage anyway. Good catch.