So this question is about what spell level to use during item creation and during staff charging. I have a witch cohort who is functioning as my groups main healer. Using the cauldron hex I wish to create potions of cure serious wounds. As cure serious wounds is a 4th level spell for a witch can I create them treating it as a third level spell for purposes of the potion? I have a staff of healing. Do I need to use a 3rd level spell slot or 4th level slot to recharge it?
I'm thinking the answer to the first question is no unless there's a loophole I'm unaware of. And the answer is a 4th level slot for the second, again unless there's some loophole I'm unaware of.