I understand the difference in values between your country and here so a different approach is needed.
240k km's ( 144K miles ) isn't stratosphereric for one of these cars but the amount of fluid leaks would make me think that it's had a neglected life . The cam and ,to a lesser extent, the sump are straight forward the oil at the rear of the engine may be just blow back from the sump or alternativly the rear crank oil seal which requires the gearbox removal . Depends on whether you do it yourself or pay someone as to how much of a worry these are .
The rust on the rear tailgate under the wiper and sometimes under the window seal is normal but the rear pillers would want further investigation to see what is the cause of that . I'd be suspecting poorly repaired accident damage until I was convinced otherwise. It would be best to check the trunk floor and deep into the recesses of the little pockets in the side trim jut inside the tailgate . The tank covers most of the underside so you may not see anything underneath. What is the paint finish and match like ?
Engine sounds to be running in limp mode , I've had this on my 2.0 and although still driveable it feels as if it driving at 65% . This could be a simple problem like cam sensor ,maf or several other issues ,have you tried the pedal or paper clip test on it ? This will certainly help you to get a better idea of what may be causing the poor running.
http://www.omegaowners.com/forum/index.php?topic=90581.msg1155463#msg1155463My CD spec car seats have power adjustment for up and down movement but the backrest and fore and aft adjustment is manual so that is normal.
Taking everything into consideration and without knowing how much the seller is asking for the car , I say that the car sounds to have had a fairly neglected life and possible accident damage too .
Unless I was specifically looking for an Omega Estate with few available I would pass this one by and keep looking.
Good luck.