My goal is to save more movements of some servos in order to move a robotic arm, since I have the SRAM memory of the arbotix completely full.
If SRAM is "completely full", where will you create the 512 byte buffer needed to read from/write to the SD card?
The "ArbotiX-M" is NOT an Arduino that you can order from the Arduino store. If you are going to ask questions about it here, it would make sense to post a link to it.