Hello! I think these are all doable. I can add a field to the NPC node that would let you specify the entity ID of the speaker. If not specified, it would default to the NPC that the dialogue was initiated from (if applicable, otherwise default to "???" or something similar). That gives me another idea to eventually add - further customization of the NPC node where you could enter a custom speaker name (and portrait once that feature is there) that would show instead of referencing an existing entity.
In regards to the NPCs not moving during dialogue, are you referring to all NPCs in the scene, or just the ones that will are engaged in the current dialogue?
I should be getting several more new functions released this evening and then I will take a look at these features in more detail. :)