I store my 6.7 all winter also.
In addition to what you are doing, I add stabil (for diesels) on the final fill up in addition to the diesel conditioner. I also add a 1/2 amp "Battery Tender" to one of the batteries (been told it takes care of both at the same time).
Been adding stabil and Battery Tenders to cars and bikes for a couple of decades and it seems to work well. Goes in, in November and out in March/April, all depending on the snow.
2013 F350 SC Lariat DRW 6.7