I think you're right about the angels (like, afaik the game never really explains where the whole exphere thing came from), and I don't know what specific thing about Lloyd's father you're referring to, but the Eternal Sword thing is kinda explainable.
Basically it doesn't matter that it's a sword. That's just the form it takes, for the intents of the story it could literally be anything else, a broom, a cactus, a bag of marbles, whatever (it just happens to be a sword because swords are cool and so Lloyd can use it in his Mystic Arte*). Like, first and foremost it's the power of the summon spirit king distilled into a material form that can be used by mortals. Basically, your run of the mill artifact of divine power, like the Triforce, the Dragon Balls, the Chaos Emeralds, whatever.
That's why it can split the worlds. It being a sword really has nothing to do with it.
*Or rather because it was a sword in Tales of Phantasia, to ensure Cless could equip it, but same thing really.
Basically it doesn't matter that it's a sword. That's just the form it takes, for the intents of the story it could literally be anything else, a broom, a cactus, a bag of marbles, whatever (it just happens to be a sword because swords are cool and so Lloyd can use it in his Mystic Arte*). Like, first and foremost it's the power of the summon spirit king distilled into a material form that can be used by mortals. Basically, your run of the mill artifact of divine power, like the Triforce, the Dragon Balls, the Chaos Emeralds, whatever.
That's why it can split the worlds. It being a sword really has nothing to do with it.
*Or rather because it was a sword in Tales of Phantasia, to ensure Cless could equip it, but same thing really.