I would never say the closed bolt hopup is stellar in any way. It's an evil consequence of that model.
It's actually a very simple hopup...but it is certainly erratic. Personally...I mod my hopup rubbers. Mine do shoot very straight (latest modded one was tested out this past weekend).
The range is not as good as some other rifles. My PTW, my buddy's FAL, and probably a host of other rifles shoot further than my WE M4/PDW.
It is not a "magic" gun...it is not the be all and end all of an airsoft gun. It does offer a lot of fun per trigger pull. That's why I use it.
The white spacer creep has been written up many times...and fixes/solutions to that.
Don't know what tube you're talking about...buffer tube? Why would you pack it with paper?
A new hopup won't do much...lots of guy have said good things about the stinger one (and they're certainly better than the stock one).
The propane nose you're getting is from the gas being used by the blow back cycle...there's nothing wrong or that can be done about that. Oil seeping between the receiver indicates that you're oil is lubed in your mags. You can back off a bit on how much oil you're using.