hmm seems to me you & your guitar are making that unpleasant 5-6k fizzing (in that mic position) and you are dutifully recording it.
tried other mic position tweaks? tho your ear height one still exhibits the problem a bit so thats what made me think its likely to be the source.
8 inches may just be a bit too close for those strummy transients & its a bit too much. it could perhaps be a levels/input chain thing, but we know nothing of your chain so assume its clean. that could be tested with another guitar/source to see how its 5-6k is captured.
otherwise put that martin on the table and test for anything out of whack.