I'm confused. Why does everyone like fallout 3 when it had only 28(?) quests and why don't you think that Skyrim can recreate this?
Because the quests were much longer and more detailed than oblivions. There were also a batch of untagged quests, that didn't involve quest markers which are probably not included in that tally. Either way, it didnt feel short of content - which is one reason why this "140" number is irrelevant.
1) Its entirely based on supposition (and possibly incorrect supposition at that)
2) We don't know how detailed the quests are. I suspect less than Fallouts. Are they just fetch quests? Do they have multiple outcomes?
3) Its not confirmed by any official source.
4) Doesnt factor in Radiant quests
5) Its irrelevant. Quests form a part of the content, but I think its safe to say that there will be more than enough to do in Skyrim.