Some of what you're mulling over involves which material to use, while other
questions involve marginal differences. However, adding a second "method" in
addition to internal insulation can make the benefits add up to more than
the sum of its parts. Not really in terms of insulation factors, since that
would defy the laws of physics, but in terms of comfort and peace of mind.
So....have you considered new siding, and adding Tyvek underneath it? That's
the silver stuff you see houses covered with before the siding goes on. Do
that, along with whatever insulation you choose, and you're gonna have one
snug house.