1) It depends. Being fictionhearted is pretty much wanting to be a character or fictional creature in a way, but you don’t necessarily have to want to have that person/creature’s physical body in your life now. You may connect to their identity in some other way.
2) Absolutely. The mind is a very weird thing. Scientists have done experiments where they can temporarily induce a phantom limb in any “normal” person, by hiding their real limb, substituting a rubber limb and applying physical sensations to it.