The phantom power measures 51.4v at the unit and 51.v3 at the mic (inputs 1&2) and 50.4v at both the unit and the mic (inputs 3&4).
This is slightly high but well within tolerances. There shouldn't be able voltage drop across a short-ish cable -- if there is it suggests the cable has significant resitance which isn't a good thing!
The phantom voltage at thge mic will be lower when a load (mic) is connected because the current flow through the output resistors with generate a voltage loss. It should be between about 32 and 38V for the Rode and Neumann, respectively.
Might the voltage from the AKAI be too high for the mic?
No, the phantom spec is 48 +/-4V -- meaning 44-52V is the tolerance range and your system is easily within that.
Your current measurement (presumably shorting between pins 2/3 and 1) of 7mA indicates a healthy supply too.
Technical Editor, Sound On Sound