Behavior of ai is not always predictable..

..so the following is based on my experiences, not necessarily fixed 'rules'.
1) If parking is not available, the typical behavior is to land at the destination, stall on the runway and then disappear.
3) Slider shouldn't make a difference. It effects the number of ai spawned. not their behavior, at least not after takeoff.
2) This might be possible. Nearly all WoAI flight plans use a fixed arrival time at the gate. The in-flight time may be unrealistic, compared to the design cruise speed of the FS model. This might cause them to jump ahead if they get to far behind the schedule, particularly if late departure is involved.
Default flight plans are calculated on the design cruise speed so there should be no need to jump ahead. Maybe try following a default flight and see if the same thing happens.
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AI 'pilots' are a very cautious lot. They do not like player aircraft flying to close, particularly during departure and arrival manuvers. If you are to close (within a mile or two) they may not make their turns to stay on course. If they are 'forced' to far off course they will eventually disappear.
What sim version are you using? Most of the above is based on following ai on 'calculated arrival' flight plans in FS9. I'll have to experiment with the WoAI 'fixed arrival' flight plans in FSX.
Dave
At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation.