Probably to expensive to put into cider. They pay a yearly fee to the developers of the apple to have it on a farmers land. Good old lot 1819. In theory it should make a better juice than honey crisp.
I use one can per 5 gallons. If you are running 6 then you'll want to do the more traditional primer. Also this just adds extra apple flavor not sweetness. See the stickies post on pasturation for sweet bubbly cider
I've never heard of that. At my climate in the winter I can get some long fermentations at 50 degrees. But I'd take a hydrometer reading and see what it says. It may be gas releasing due to pressure changes.