Thank you! That file lead to Pssive Inheritence Rate and "IKE_PASSIVE" on line 1821, editing the value of 10 there doesn't do anything, but searching for IKE_PASSIVE lead to データ.ks, where the ritual data seems to be stored. Most of it seems faairly obvious, each level providing a "power"=>"(number)" associated with it, turn numbers ranging from 0 to 120, traps from 2 to 3, etc. and notably Passive Inheritance rate from 10 to 30! Edited each level of that to equal 100 instead of 10/12/14/16/etc., and loading up the game again shows it works even in existing saves!
One thing of note is that the atk/def/mgc/com upgrades all have power 0, but given that was available in Burrow 1 I'm just assuming it's functional but handled by a different file or something like that