As promise, I made a test of your file.
By replacing the hal_ext_lld.(h and c) files with your files, the testhal/AVR/MEGA/EXT is not working any more.
With the current driver, this demo works for all the board whose are currently supported (uno, mini, nono, mega...) so for the moment I do not bump your changes.
I suspect that PCINT for your device ATMega162 as to be manage differently from PCINT of the ATMega2560.I will read and compare the two datasheet to see if there is any differences and explanations of why it is not working.Did you also use the ATMega2560 datasheet when you implemented the driver?
Also you files looks the same as last time, what did you change this time?
I do not have a board with the mcu you are using so I can not make test to the some board.
Any way I'm still working on to integrate the PCINT support on the driver.