Your dives wont be that long or consume that much power. 160wh will be fine for ~90mins of diving IMO and I am very cold sensitive. Alternatively you could bring 2x 90wh batteries.
Cold sensitive diving in WA? For this trip anyway, it seems there will be plenty of time to recharge in between dives if I even use most of the charge on dive 1, so I'm less concerned about the total WHs now. I'm pretty cold sensitive, but not like my wife who was in 6mm neoprene in the Caribbean at 83 deg F.