Open console and enter this:
$CorpseTimeoutValue = 60000;
That should make corpses stay for 1 minute.
To change the item time, try this:
$a = 30000; $Game::Item::PopTime=$a;$Item::PopTime=$a;$ItemTime=$a;
That should change the item time to 30 seconds. (I'm not sure which variable is the correct one, so I just included all of them)