You can unsummon by clicking on the doll again in your inventory (ie you can toggle the summoning doll on and off by clicking the doll statuette repeatedly). This can be useful to avoid the time penalty when re-summoning right away if the doll is otherwise unsummoned (by using an entrance, teleporting, being killed or running out of range).
The clerics' Disease spell should wear off for the summoning dolls as well. Maybe part of the problem is that the skeleton doll starts off so weak?
Can you try a stamina potion, to see if that helps the doll? It should at least allow it to move, and may kick start the normal regeneration.
