For the heat death - I understand it enough for not to believe you that some living things cant survive the heat death in anabiosis
For the existence of other universes and the chances of new universe being created:
The theory of the big bang says that the univese exploded long long time ago and is now enlarging like a baloon.
The theory of the multiuniverses says there are more than one baloon inflating at the moment, and there are new baloons exploding. Some baloons enter in each-other and unite, others fision in halve, divide and turn into two universes, third die, fourth explode newely. New universes are being born even nowadays, and people hope even to see the baby universes with new telescopes.
https://www.youtube....h?v=QzIbpwcm0pk
For if people will be immortal some day:
I believe, that the human mind is cappable of solving all problems. If the solution of the problem is not currently available, it will become available in the future.
We both will live forever if we destroy the nearest threat - the aging. And if we continue to destroy or overcome the new life threats.
For the both body and spirit concept:
Its yor time to prove now. Prove, that we are both body and spirit and not only a body.