Sending MSB and LSB for channel volume to their respective cc channels, I admit, is beyond me at this point.
CC message 07 is the most significant 7 bits of the volume, message 39 is the least significant 7 bits. Together you have 14 bits to control the volume. So suppose you have a variable called vol that contains a 14 bit number, that is a number from 0 to 16383. You split it up and send it over two CC messages
vol07 = vol >> 7
the variable vol07 is sent as the value of CC message 7
vol39 = vol & 0x7f
the variable vol39 is sent as the value of CC message 39
I also tried using note on at 0 velocity, but I'm not sure whether this is a correct implementation of running status.
It is not.
Running status means that after the initial note on byte and note number and velocity number subsequent notes are just represented by the note number and velocity number, the note on byte is missed out.