You can accept certain things on faith, but to claim that your brain can actually know what it cannot compute is the height of arrogance. It's the same arrogance displayed by Richard Dawkins when he says "science" "disproved" God.
Well, we really accept EVERYTHING on “faith.” Subject the entire field of how we “know what we know” to the same skepticism that you subject God to... and you become a very inward turned solipsist.
And let me add, an unhappy solipsist.
How do we believe in radio waves? We performed enough experiments to show that this was eminently believable. We never proved that these weren’t invisible goblins.
Anyhow, God is also eminently believable. God has furnished a reason why we have such trouble believing in things God... it’s because of what is called sin. Sin is shutting out God’s blessings, seizing Satan’s curses in their place. And it is an unrecoverable situation without salvation. Go ahead and quibble about your doubts all day long, but when you believe and trace where the belief takes you... you will find God is no less real than radio waves are.
Also I am not claiming, as you do, that our knowledge is limited to physical brain! I am one of those pesky spiritual folks who tells you about a soul.