MDG: So when does the killer get the protection of the Ir Miklat (from Goel Hadam) *only* as long as he remains in the Ir Miklat?
AFAIK, Yes.
An, unintentional killer, who was not negligent (e.g. upswing of the axe), get protection from being in the Ir Miklat. Completely accidental (Ones) goes out free, and the unintentional but negligent (downswing of the axe) is a “marked man” with no refuge available. Col sheKain an intentional killer is a “marked man”.