Electronic – Why does the Datasheet for the ATMEGA88 have two pins for PORT D bit 5 (with different functions, too)

Atmel makes a 32-bit 60 MHz AT32UC3B1256 AVR microcontroller with 256K of flash, 32KB of RAM in a 48-pin TQFP package. That's as close as I could find to your specs.

It looks to me like the wiring on the PCB matches the chip pinout that you show — why do you say that it does not?

In any case, ADXL345 is the part number of the chip itself, which is made by Analog Devices; get the datasheet from them.

It doesn't seem as though there's any documentation on the PCB itself, so it looks like you'll have to assume that the signal labels on its pads correspond to the pins with the same names on the chip. You may need to do some reverse-engineering to figure out exacly what all of the other parts they've added are doing. It looks like there's a 3-terminal regulator and some bypass capacitors on the left, and some pullup/pulldown/termination resistors and an LED for various signals on the right. This is why you should never buy a board that has no documentation.