I have a possible solution to my own question no. 2. Tell me if this makes sense:
The reason that the bike worked pretty well although the front cylinder timing was off a full crank revolution is this - the spark plug fires at every TDC and since I'm carburetted, there was always air/fuel mixture to be drawn by the vacuum.
The reason my friend's 990 worked on one cylinder only in the same situation is that his bike's fuel injector only works every 2 revolutions.
Does this make sense?
This could also explain why my bike sounds like a single cylinder at idle (and also sounds as if idle is slower significantly than the 990), because the power strokes are not spaced further apart like it should.