Rewatching Ep. 2 and something stood out. When MiB is sitting with Lawrence and threatening his family (ultimately killing his wife), he says (paraphrased) "you and I have been through a lot, we fought off Ghost Nation braves...etc". And then we actually see that in episode 7 when William and Lazo fight Ghost Nation after the train. Further confirmation that William = MiB.
Rewatching Ep. 3, which has several Bernard/Dolores scenes, and I'm now absolutely convinced that Bernard is Arnold or at least a clone of him and that all "Bernard"/Dolores scenes are in the past as Arnold. Dolores is clothed, they're in a satellite hub, and Arnold is mulling over reverting Dolores but can't bring himself to do it. From here, it's clear that Arnold dies and Dolores almost destroys the park. Also, the "Bernard" scene with his wife is actually Arnold in the past.
I love this show so much.