Someone tells me, "1 + 1 = 2."

I tell them, "Ah, but if you take one cloud and another cloud, and add them together, you still get one cloud, so 1 + 1 = 1."

Neither claim is "silly bullshit", but the conclusion of the second sentence is clearly broken. I have no reason to doubt Feser is a domain expert in theology. It's what he does with his expertise that bothers me.

Anyway, if it takes such a round about sequence of obscure studies to even begin to make sense of this stuff, it is no wonder that modern atheists (or virtually all Christians, for that matter) have trouble getting it right.

That's exactly the point. Christianity is already a sociological fact that bares almost no resemblance to whatever kind of Christianity it is that would "get it right."