Porting D1 to D3, Vector Grafics and RDBMS

Hello everybody,
As a Newcomer to Delphi and DB2 I directly dropped into "deep water". I have
to tune a complex Delphi 1 Application (>> 100 000 lines of code). The
runs against a DB2/2 Database Server via ODBC and CAEDOS. The Application
holds vector grafic objects in a relational database schema (which is of
course not optimal) and has to render the vector grafics on the client's
screen. There are severe performance problems in reading and writing all
records belonging to one grafic object as well as in rendering.
I did some investigation of the code but did not find any severe mistakes or
inefficencies but a lot of optimization, so I think it must be the overall
architecture of the system which produces the problems. Thus I need some
hints and comments for proceeding in my work. Here are my questions:
1. How much Perfomance improvement will I achieve by migrating from Delphi 1
to 3 ? Will the migration improve database access also? Are the any concrete
experiences with DB2 Database apps ?
2. How much will database access be accelerated by the new native DB2
drivers (as opposed to ODBC and CAEDOS)?
3. Which problems will I face in migrating the application from Delphi 1 to
3 ? Will a recompile do it :-) ? Are there any concrete migration concepts
available ?
4. I'm sceptical whether DB2 and OS2 Warp Server is a good choice for
massive parallel and interactive (as opposed to batch mode) applications. I
would prefer NT and SQL Server or Oracle but I don't have any direct
comparisons at hand. Are there any Benchmarks or reports on this subject?
Are there any recommendations regarding backend Server, RDBMS, and Network
for Delphi Applications.
5. Any Hints for Perfomance tuning for rendering of vector grafics ?

Any help is appreciated,
Thomas Mahler