IP option setting and increasing MAX sockets

Hi,

I have to do two things for validating our proxy product.

host ------proxy ---------- server

1> Everey TCP packet will have proxy as destination and origional
server address in ip options, how I can simulate/test this in linux?

2> We need to test proxy ability for 25000 simultanious connections, I
used ab tool, for small files it went upto 1000 max connections, for
larger files it was only 300 connections :-( Any help on how I can
increase open files (socket) in linux, I need to download bigger files
as I have to see the connections are alive atleast for a minute.

Thanks,
Prasanna.