you've got 18 years

There is a secondary possibility to extend his life.

He can kill his child.

Obviously we both know this wont work. Either the child will cling to life, or the mother will sacrifice herself. Make sure its the former, so the mother can still raise the child. And OP should then leave, with that armor and swords he made, and go join some lowly bandits nearby.

Before a decade goes by, he'll be leading every bandit, knave, thief and assassin in the next three kingdoms, and he'll be giving his child a BBEG to hunt down.

Bonus, OP can send the weakest men he has to kill the hero first, and slowly ramp up the skillset of the villains sent, giving the hero practice in the combat arts. That way, when the big ending happens, the only true name the Hero will need is "Father."