Inverness is approx 2 hours drive to Aberdeen , same time more or less on the Train.
I beleive the reschedule means that the flight is going back to operate on the INV based Q400 (with INV Crews) as opposed to a MAN based Q400. This has been the historic schedule for the Day6 INV-MAN and only changed for the Winter timetable.
Schedule changes are frustrating I appreciate but dont believe ABZ would necessarily be a better option given the extra distance.
True that the INV-BHX operates a couple of hours later than the retimed INV-MAN.
Your going to a truly beautiful part of our country. Enjoy.