If you insist on using words in a way other than how that word is intended... you will forever continue to be confused as to why others cannot understand you.
Belief in God certainly can be "internally certain." But it cannot be "internally and objectively certain."
It can even be "as internally certain as I am about other things that are objectively certain." But it cannot be "internally and objectively certain."
Because there is no objective certainty about God's existence. If there was... it would be on the same level of "a flat earth" conspiracy.
Calling a belief in God "internally and objectively certain." Is like calling a gas-guzzling muscle car "loud and environmentally friendly."
If it's a gas-guzzling muscle car - it cannot be environmentally friendly, an environmentally friendly gas-guzzler does not exist (at our current level of car-technology.) If it's a belief in God - it cannot be objectively certain, objectivity about God's existence does not exist (at our current level of God-knowledge.)
I am quite clear that you claim to give my concept of God no more thought than you would Zeus. I get that.
Do you understand that atheists give your concept of God no more thought that you (Phat) would give to Zeus? Do you understand that many/most people, a few thousand years ago, would call their belief in Zeus "internally certain?" I'd even be willing to bet that most of those people would also call their belief in Zeus "internally and objectively certain" ...for as much as that means.