OD&D (really FMC) Like it's 1974

I have been running Caverns of Thracia with Fantastic Medieval Campaigns for quite a few sessions1, and just about every session I have to stop and discuss with the players about how to proceed with a ruling. In the spirit of FMC, I have been doing my best to avoid backporting modern D&D-isms into the game. In fact, where reasonable, I do my best to make my interpretations different from later rpgs. So, without further ado, here are a bunch of my rulings for FMC: All HD are rolled every level—if lower than current hp, increase hp by 1 instead. Prime Requisites: A magic-user’s prime requisite score is equal to their INT, plus 1 for every 2 points of WIS above 9. (So a magic-user with 12 INT and 11 WIS has a prime requisite score of 12+1=13. This does not require that the magic-user lower their WIS, unlike in B/X.) A fighter’s prime requisite score is equal to their STR, plus 1 for every 2 points of INT above 9, plus 1 for every 3 points of WIS above 9. (So a fighter with 13 STR, 13…