I don't believe I have a measurement for that. It has to be a light pressure. You could clamp your hand and it would not be painful. The boards help to protect the mould from deforming as well. The clamps are substitutes for your holding the boards yourself, for safety reasons when pouring liquid metal. So a firm grip without strain is enough.
The mould should simply be dry and warm to the touch. The goal is to prevent premature cooling of the metal. Room temp should be fine if that means its warm.
Do your clamps have a specific clamping pressure, so it does not deform the mold?
I don't believe I have a measurement for that. It has to be a light pressure. You could clamp your hand and it would not be painful. The boards help to protect the mould from deforming as well. The clamps are substitutes for your holding the boards yourself, for safety reasons when pouring liquid metal. So a firm grip without strain is enough.
Will room temperature suffice or should the mould be hotter before casting?
The mould should simply be dry and warm to the touch. The goal is to prevent premature cooling of the metal. Room temp should be fine if that means its warm.