Old SPI protocol help

Hey guys I have a old LCD driver that I'm working on replacing. It has 3 input lines: Data Clock and Load. In the 1st picture they are MOSI, SCLK and SCS respectively. The Load data line does not behave nor have the same purpose as a SCS line in the SPI protocol.
I have tried to make an Arduino SPI slave to replace the driver and instead convert the data and display it using a different display. I've been using an Arduino UNO but I cannot get a consistent read (the other picture shows serial monitor output of the Arduino SPI slave program). It seems that the clock frequency (~70kHz) is too slow for the Arduino. In addition, since the protocol is not really SPI the code is not reading the data correctly.

I need some help and wanted to see what you guys would recommend. If its a good idea to continue the SPI path and try to figure out how to change the Arduino library to conform to the protocol or if there is some other device that is better suited for this.