The new coolant hose arrived and was fitted relatively easy. The cooling system now seems to be leak-free.
A set of Bosch spark plugs also arrived so I fitted those as well.
During the test drive the idle/stalling problem still occurred but seemed slightly better, prompting thoughts about the issue being ignition related.
I ran VIDA again and this time the misfire code had returned: "ECM-3502 Misfire, emission related - Multiple cylinders".
I then looked at live misfire data in VIDA and could see misfires being recorded when the car was idling badly (video below). No misfires were recorded if the car was not idling, like when I held the revs at around 1,000 rpm with the throttle pedal.
The misfires happen on all cylinders but more so on cylinders 2, 3 and 4.
I swapped around coils (3 to 1, 4 to 5) to see if the problem moved away from cylinders 3 and 4, but it did not.
(video shows it idling on its own first, then me revving it a little and trying to hold it around 900pm, then letting it try and idle itself again)
The photo shows the data after swapping the coils around.