Merchant Miki is still in New Leaf City, on the platform above the NLC Mall.
I also recommend getting a Jr. Boogie familiar, which heals 15% MP every 10 seconds.
Arcane force itself is a kind of prequest to training maps and end game bossing, a really long and repetitive one at that. It makes absolute sense for AF to carry over your characters.
I personally wouldn't mind if Arcane Force was account wide, but just Arcane Force, not symbols; the other bonuses, like stats and even the damage bonus from having high arcane force are too powerful to be a one and done a day, they'd have to be tied to something like actually having the symbols themselves. I have like 30, almost 40 characters over 200, and at least 10 5th jobbers. I don't think it's fair to get thousands of stats and a damage bonus on all those characters on what amounts to just 30 minutes a day for me.
This would be more like the new blockbuster change, not what OP is asking for.