I could read stream 1 (8-bits) with a command of "stream1 = fread(fileID, 113:3600112 '*uint8')".
No, do not do that. Instead fseek forward by 112 bytes from the beginning of the file, and fread with size 3600000 with *uint8.
For the second group you do not need to move after the first group. fread 3600000 elements using 'ubit12=>uint16'
For the third group you do not need to move after reading the second group. Do the same fread 3600000 'ubit12=>uint16'
I was concerned because the majority of time that data structures are spoken about as 12 bit, really what is meant is using 16 bits per sample with either the 4 MSB or LSB unused. However the sizes work out perfectly for it to really be 12 bits per sample.