I would guess the reason you haven't had any replies is because they are particularly difficult questions to answer!
I'll have a go. I only have very limited IFR experience, and I've never yet done an approach in actual IMC, so I'll limit my answers to visual approaches.
1) With very low hours (e.g. as a student pilot), the high workload of getting everything done downwind was hard. The roundout/flare was impossible. As I became more experience, the downwind checks became second nature, and the actual landing became hard. As I moved to faster and more complex aircraft, the landing itself has gradually become easier (but certainly isn't easy) but the downwind checks get harder with each additional complexity.
2) Life is a lot easier if you try not to combine things.
3) I really can't answer this question very well at all. Flight management tasks should hopefully be complete by the time you're on the approach, except for the approach and landing checks. Manual control will depend on the aircraft, the airfield, the weather, the traffic and many many other factors. Scanning and monitoring will again depend on lots of factors, mainly the level of traffic. And ATC will depend on lots of things - many of the airifields I fly to don't have ATC at all (but communication may still be just as important - possibly even more important - than at a controlled field, depending how busy the field is).
4) It is not the factor itself, but the intensity of the factor which is important. A bit of weather shouldn't cause any concern, whereas serious windshear at 50' with a crosswind that's near limits will (and I'd guess this is even more important on an instrument approach). Having stayed up late because you wanted to watch the end of the film last night shouldn't cause any concern, but the only time I've damaged an aircraft while landing it, one of the main reasons was fatigue that was well beyond staying up late to watch the end of a film.
Hope that helps with your study, even though I can't directly answer any of the questions.
FFF
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