Hi Ben,
the pin-configuration of your PCB is right. Read my first answer again:
RXD is used for the data-transmission and TXD for the clock!
To your second question:
you can transmit just 8 bits at one time. There are only 8 pulses on the
clock line.
If you want to send all 32 bits at one time you have to split them up
into 4x8 bits, then send the first byte, wait for end of transmission,
then send the next.
In this case you don't skip any clock pulses but you get a pause on the
clock line because of the time you need to get the end of transmission and to write the next byte to SBUF.
As far as I know the clock has a duty cycle of 50%.
If the driver can't work with the pauses on the clock line you have to do
the whole thing by software using the pins that are already connected
to your driver!

Christian