To him it has been 100 years, but to her it has only been 10.
I was mistaken about him not having any useful skills in his first round in this world; he actually had them, but it was all mundane daily life skills that were extremely useful, just outside of battle. It seems he was genuinely kicked out due to his party underestimating his value. Then with him in the party, they couldn't have gotten betrayed in that manner and maybe they had a chance of winning (without Ed adding to combat capability since he wasn't OP yet back then).
The hero of this world was far from perfect, but died a hero in the end. He might have failed to save the world, but he managed to save at least one person before he died. Seems he's not quite the typical irredeemable arrogant scum in most banished fantasy stories.
I still don't believe he can go to world 0 just from this world. So I see a potential pattern for this story: Ed (and Tia if she sticks around) will do one more round of world-hopping, fixing whatever happened after he got kicked out.