Yes, auto iso is available in Manual mode. Also, when shutter speed and aperture are set in a Custom Mode they remain "sticky" when you return to that mode unlike the GH3.
Thanks, nice! Is there any way to compensate exposure in Manual-Auto-ISO mode other than through the ISO button > fixed setting? If I were designing it, I'd link the EC button to ISO in Manual, so you could stay in Auto-ISO with offsets.