For the question about deep sleep not being supported on the mDot, please see the section “Deepsleep functionality change” on page…
https://developer.mbed.org/platforms/MTS-mDot-F411/
I believe the hardware team designed in JP5 in order to ensure the xDot could be isolated from the developer card prior to having a complete understanding of what could be accomplished in software. In software, we are programming the IO as analog no pull. So leaving the connections in place (JP5 removed) has no impact on power draw.
I have tested a couple xDots using the AT command application and I am measuring 1.6uA in sleep. The AT command application can be downloaded here: http://www.multitech.net/developer/downloads/#xdot
Can you try that and see what you measure?
Kind regards,
Leon