Can't really say much about the spring piston guns, since I've not worked on them much, but, I can say something about CO2 guns that might add to the discussion. I've worked on certain CO2 rifles that had a restrictor plate installed; presumably to reduce the output energy. However, what happened was that the CO2 flow would encounter this restriction and reflect backwards and reopen the exhausts valve so that the rifle would "chatter" with multiple openings of the exhaust valve.

The lesson here is that the forces involved in an airgun are not just simple physics. It's not just the size of the pellet vs the piston. Instead, there are forces vectoring/reflecting off any surface in the way of the moving air/gases. Especially if the forward end of the piston housing is straight, the forces produced by the combustion could hit it and directly reflect/vector back against the piston.

So, 1) the weight of the pellet and or how much resistance it produces to forward air/gases would probably make a difference.

2) I'm pretty sure that an experience airgun smith would be able to determine if a gun has been subject to repeated dieseling; there's going to be residues from the combustion.

3) can't see why not. Lot's of variables would be involved; amount of dieseling, shape of the "combustion" chamber, resistance of the pellet, strength of the spring....