1.: The QT Documentation is quite comprehensive. Additionally there are books and tutorials for quite a few things on the web.
2.: Don't know
3.: If you use konqueror, install kdeaddons. That will enable an extra toolbar with a function that allows you to save a page with images included. If you want to mirror a webpage there is the commandline tool wget. It allows mirroring with -m. Make sure you limit recursions and some of the other options or you'll end up with a mirror of the internet on your harddisk
4.: QT is quite nice to program with. IMHO it's the nicest C++ class library I came across yet. There are also tools that allow more rapid gui programming based on gtk. If you want really rapid gui development in a style similar to VB on windows, try PyQt. You can program plattform independant QT based qui apps with python. Of course there is also Kylix wich is free for noncommercial use. It also uses QT. There is an annoying popup though.
The best way to improve the kdevelop documentation is to write manuals about stuff you found out and pass them on to the kdevelop developers. I'm sure they'd appreciate your efforts.
If you need help on topics you can't figure out otherwise, there are Mailinglists for developers using QT. If you develop KDE apps you can subscribe to kde-devel. The folks there are usually eager to help you if your question isn't answered in the first section of some obvious FAQ.
Hope that helped a little.