Well, what years are these vehicles? The later skyactiv engines had a redesign that keeps the intake valves hotter to help burn off the carbon. I wouldn't mix transmission fluids, I would just use what Mazda says to use. These transmissions aren't cheap to replace so I wouldn't risk putting anything in other than their recommended fluid.
Q&A With Dave Coleman - Mazda Engineering SAVAGEGEESE : Exhaust Manifold with integrated flaps/butterflies (bolted to head before turbo): Are they pressure actuated or electronically actuated to...
Well switching to synthetic would not hurt. And review owners manual. Is 109F considered severe service, if so follow the severe service section for vehicle maintenance.
I assume batteries will not last more than 2-3 years.