Sorry, just saw your reply now while scrolling for something else
Lemmy.cafe is defederated from the entire triad, which is the allure.
Migrating a comm isn't too involved, all old content stays in place but the comm gets locked for new posts to mods only and you change the display name to something like "Moving to X comm" (search for the television comm for an example of when !showsandmovies@lemm.ee moved)
Looking at the comm, it looks like you have 3.4k subscribers, but only ~500 of that are .ml users. But subscribers are a very poor metric, because that number is often inflated with dead accounts. Especially considering .ml's age and the comms age, id say the bulk of those subscribers are long dead accounts.
Going by MAUs, !fantasy@lemmy.ml is currently at 66 users. !fantasy@lemmy.cafe is at 23 with just what I've crossposted there, so any kind of focus on it will quickly grow past that
Plus, .cafe has had a bit of a...cafe feeling to me so having a fantasy comm on it feels rather fitting
Alternatively, you could recreate it on literature.cafe which does fed with .ml and might be even more of a fitting instance and I'll close this one in response