It seems that you have not compiled your gtk with XInput-support. Please rebuild gtk and use ./configure --with-xinput=xfree for building the Makefile. Then do a make && make install. Then rebuild your gimp so that it uses this extendet gtk.
Yes, it generates button 4 and button 5 events.
read the section about Serial_Num
Read the section about buttons.
You can not use the intuos macro area, sorry.
Only Artpad / Ultrapad Macro stripes work. Read the section about Gimp Keys.
Yes, read the section about the Top... Statements
Yes, read the 'Port and Device' section
This mostly happes under the following condition:
AllowMouseOpenFail was specified and the device is set to /dev/null. Set the device to a nonexisting file instead, for example /dev/fake, and you will get back your CPU time. See the examples for this under the 'Port and Device' section.
Another reason may be that there were too many interrupts produced.
I was told, that hdparm -u1 /dev/hdx (replace x with your drive letter) may help.
Most Graphire's are known to be weak for that, intuos seems to be better but still not perfect. This seems to be a hardware problem.