Thanks for posting all this valuable information.
For your problems with the LEMO keyboard connector check the signal levels on the data input.
The keyboard input uses TTL logic levels but there is a very heavy internal pull-up resistor on the 4041 keyboard serial data input. You will need to sink about 20mA to get an adequate logic low level and, although this was OK when driven with the older bipolar TTL devices, most modern CMOS-based interface chips would struggle to sink this much current.
