#1. This is a limitation of Word, not SharePoint. There is one 3rd party
product that I'm aware of which will allow you to divide a document  into
sections and work on the sections  independently from each other, but store it in
SharePoint as though it were a single document. But I doubt you would be able
to use it without involving the SP admin  and IT department. You can read about
it here:

www.blackbladeinc.com/.../default.aspx

#2. No way to change the versioning support without custom programming.

#3. I would suggest two books. Microsoft(r) Office SharePoint(r) Server 2007
Administrator's
Companion<http://www.amazon.com/Microsoft%C2%AE-Office-SharePoint%C2%AE-Administ\
rators-Companion/dp/0735622825/ref=sr_1_4?ie=UTF8&s=books&qid=1244066466&sr=1-4>
by Bill English and Microsoft SharePoint Products and Technologies
Administrator's Pocket
Consultant<http://www.amazon.com/Microsoft-SharePoint-Technologies-Administrator\
s-Consultant/dp/0735623821/ref=sr_1_2?ie=UTF8&s=books&qid=1244066519&sr=1-2> by
Ben Curry.

Microsoft Office SharePoint Server 2007 The Complete Reference

Microsoft Office SharePoint Server 2007 Best Practices

Microsoft Office SharePoint Server 2007 Administrator's Companion