I set the ride height on my 67 coronet to the factory specs, considered going higher (lol) because of the SS springs in the rear (waiting for them to sag now!!!)
I have a little more space between the frame and the bump stop than the OP.

1-1/8" difference measured from the bottom of the TB adjuster blade and the bottom of the balljoint body if I remember correctly.

looks like the TB adjuster is already screwed in pretty far...depending on the purpose of the car, maybe it's time to bump the TB thickness up a bit, especially if you want the front pretty low.

is that bump stop designed to be a slightly progressive stop? perhaps a small amount of contact there is ok.