As usual we segue off-topic, which is part of the joy of this kind of forum.
So to go to the OP, parma has to be extended before anything goes wrong. As the parma is roughly a 2 minute process, it cannot be adjusted on the fly as Parma currently works. It would require a hermetic breakthrough to change this.
The parma is the signature achievement of the order. Anyone having a breakthrough which improves the parma would be the most celebrated mage of their age (and require a generous SG).
The only way to protect against a Pilum for a mundane with short notice would be a fast cast defence. Being at range it would be a largish number. Long term, create an item which grants fire immunity.
Ars Majica, I consider distance is always vague.
Other games, the ball of fire is a very specific shape and one can have it stop so the 2 grogs fighting the 2 monsters don't even have singed eyebrows, while the monsters suffer the full fury of the flames. That works for those games, and those games would suffer without everyone having an internalised protractor, compass and slide rule.
AM is less fun and less interesting if all weights and measures are perfect. I would advise not to play AM with a grid map for example. Using minis without a grid, would work. Obviously my opinion, and I'm not saying people using grids are doing it wrong. Whatever works for the group.