I agree with your conclusion, but --

"...perfectly empty of all thought, reflection, conscience, and consideration, entirely destitute of the knowledge of God and Christ, unable to look backward or forward, or inward or outward..." (emph, added)

How does someone believe they are empty of all thought when they can't look inward? I smell a rat.

A zombie's behavior will be identical to that of a conscious counterpart; see "Zombies" (Stanford Encyclopedia of Philosophy):

Zombies are exactly like us in all physical respects but have no conscious experiences: by definition there is ‘nothing it is like’ to be a zombie. Yet zombies behave like us, and some even spend a lot of time discussing consciousness.

The "zombie" preacher clearly has some sort of psychological disorder, which is precisely your conclusion. Having a psychological disorder doesn't exclude him from being a zombie, of course -- if zombies are possible, it's possible that some of them have mental disorders, or even believe that they have problems with their consciousness -- but it sounds like in the first part of your essay you are trying to explain the preacher's condition with his decent into zombiehood.

There's no empirical way to determine whether someone is a zombie or not. That's the whole problem with zombies.