I’ve shot a charging buffalo, right between the eyes at 8 yards. Exactly where I was aiming.I think you are over thinking this.
I would personally sight in for 100 which should have you pretty close at 50. An inch high at 100 wouldn’t hurt anything.
You aren’t going to be trying to brain shoot a charging buff at 30 yards. A charge scenario is going to be more like 30 feet or less. It doesn’t matter where you sight in you will be low at that kind of distance because of the hight over the bore. Also, your shooting at that point will be instinctive. You will not have time to aim in any thoughtful way. In a charge you will need to shoot both eyes open like a shotgun.