It seems like your healer just dosnt want to be a healer but a pasifist healer almost. While that can be cool and fun he's still limiting the other way s he can assist his party other then being a one trick pony. That being said there are still some house rules you could do to assist him. Healing spell healing half the amount toal after hp to heal stamina. Example player hp Max is 12 and players Stam is at 0 and has suffered 2 hp dmg so current Hp is at 10. Healing cast spell and get a 10 total. 2 poits go to Hp the 8 remaining divided by half so stamina is healed 4 point. If player took no hp dmg, stamina would be healed by 5. Another option would be be to create spells to heal stamina. I've played alot of healers but there's more to being a healer then just healing in a game like this preventing your party from injury is just as importan. Otherwise he's making it harder not just on himself but the party to. Ask him what his character is willing to do to protect his companions.Make it into a story point and help a character show him other options he could have that don't conflict with what he wants to do. Play can get stuck in a concept sometimes and not see other options till they are show.