General Purpose fertilizers seem to work as do specific name brands or organics. Your preference/choice will be just fine at this point.

Dormancy is not limited to container grown plants. All Plumerias to some extent or another have a dormancy period.

I'll defer to someone else in your local area for climate specific practices but the best general rule regarding temperatures is to protect a young plant from anything below 40 degrees as well as winter rains. The more mature a plant is a generally results in more ability to deal with cold off season rains. In other words until your plant matures I would be more cautious than not.

Garage storage is always an option provided it is not sitting directly on a concrete floor.

Depend on plant. I have one plumeria celdine in the ground. during winter, protected by the mover's blanket (keep warm) and plastic turf (protecting from the rain), but some tips still get black tips. This winter, I am thinking placing pipe protector on the tips....

Thanks so much! the_first_kms, thanks for clarifying that they all need some dormancy period. Kawagoe, I think you also mentioned that they don't like intense sun and can get burnt, so I need to think about location. My full sun areas all face south or west, which can get pretty intense. Having it in a pot will make it easier to figure out the right spot!

KC