I realize you had complex IRL situations surrounding all of this, but the fact that warlock was openly and rudely questioning your system rather than just rolling with it, would have been enough for me to question them privately about their manners and whether this was the right game for them. It is YOUR game after all and during session it's very frustrating and disrespectful to the other players' time to relentlessly belabor the point. I'm surprised you put up with it as long as you did despite attendance from Warlock.
I realize you had complex IRL situations surrounding all of this, but the fact that warlock was openly and rudely questioning your system rather than just rolling with it, would have been enough for me to question them privately about their manners and whether this was the right game for them. It is YOUR game after all and during session it's very frustrating and disrespectful to the other players' time to relentlessly belabor the point. I'm surprised you put up with it as long as you did despite attendance from Warlock.