Check the "Note 1" under Table 3-1 in the datasheet - it states that the addresses only apply to the bottom byte of the address. Therefore you have 128 bytes (each 8-bits) of high endurance flash memory.
I'm not sure where you got the information that the 128 bytes is divided into 74 locations from. The addresses are (for your MCU) from 0x780 to 0x7ff.
Therefore accessing these memory locations is straight forward.
Also what do you mean by only having 26 bytes left? Are you saying that you have only 26 locations free in the normal programming area of flash?
Susan