From: Warsaw, Poland
1. Based on what I read on this forum about resources and their "rarity" I may say that most propably majority of players feels exacly the same - resources are too abundant. If You ask me - I am very glad that most basic resources are common and do not cause problems (basic = needed for building primitive, tech level 0 equipment), however more advanced and luxury resources are cleary too common. That is how I do feel about it.
2. If there is any way, than I do not know about it.
3. Those are resources bought by other empires, that are waiting for transportation. Sometimes buing empire get counquered before they manage to take their resources ^^
4. I do not know if I am understanding this question correctly - are You asking why some luxury resources are being demanded by colony, while other are not? If so, than it is worth to note that colony needs only 10 luxury resources to achieve 100% development (providing that other requiments are fufiled), so if they have acces to 11, they will not use one of them. I do not know however on what basies they are choosing which 10 out of 11 avilable resources they are going to consume.
I hope my answers help at least a bit :) If somebody will see that I am mistaken somewere, than please - correct me.