The mage-archeologists who found me were hunting for a "life crystal", some sort of mystical stone that won't allow anything near it to die. That's how I survived. Once rescued, I needed to be restrained and mentally healed. It took months, and then my adaption to your world longer. My long, long exposure to both ice and time have given me some unique skills.
Endurance was an ongoing problem. He managed it by not taking two Power Pool toggles which most my guys take, Manuevers (or Assault) and Tactics. The Farsight power he took at 28 was a great, non-toggle, substitute for both. At 38, he took Chrono Shift, which helped a lot with endurance recovery. When endurance did run low, he could depend on both Jack Frost (his pet) and his debuff auras to pick up the slack.
I had a pretty good idea of what his backstory was before creating him, and the goal for his costume was to make him look like a modern neanderthal.