The driver cannot cause it to pull too much paper and jam, that would be a hardware thing that is unrelated.
Getting a Fiery update for a machine that old would be near impossible now days, not sure where you could look besides ebay possibly.
Try also disabling the SNMP on the port, may make it run faster.
I have no idea how it could pull A3 vs A4, it would make sense if switching A3/A4 and Letter/Tabloid, but not A3>A4