I've been there, have played in a couple churches like that; At least he is aware that he is not very good; the folks I played with didn't really have a clue.
Is he playing elect. or acoustic? you could sneak the vol. setting down on his axe, lol! or try wearing an ear plug in your ear on the side that faces him
Seriously though, I don't know what else to say; you are correct, it does throw the other players off, & is distracting. I guess you say he is operating under the verse in Psalms; "Make a joyful
NOISE unto the Lord... He has the noise part down, it just may not be very joyful... but at least he is having fun!
It'll all work out...