There's a few very deep things on earth. The deepest ocean trench is 5 miles deep, so that eliminates number 1.
No it does not. It could be 1-3 miles deep measured from the deepest ocean trench
The deepest hole in the ground is 7 miles deep.
How is that measured? If you took a 7 mile rope and hung it down a hole that does not mean the hole is 7 miles deep. In the FE models where the earth has a bottom it could just be hanging out the bottom.
The main evidence of a super deep earth is the existence of a magnetic field. The amount of iron alloy this requires would mean the earth has to be super massive (toward the 4000 mile figure) in order to have such a magnetic field.
I disagree with this. In the FE models in which the earth has a magnetic field caused by iron alloy the amount of iron alloy to dirt ratio in that specific FE model could be higher than it is in the RE model.
In the FE models in which the earth has a magnetic field caused by iron alloy the iron alloy could be much more dense specific FE model.