Hi,
Here is answers for questions 4 and 5.
4) I enabled gateway logging, how could I catch rejecting connections from third party systems?
SMGW->Goto->Expert functions->logging
In the above path if you select security->(under that)->Rejected access only
when you select that it should show you the connections getting rejected.
5)For simulation mode you have 2 options. you can activate directly from the above path.Other option if you maintain gw/sim_mode = 1 that will make the permanent simulation mode. But once after all the entries set in reginfo you have to disable simulation mode. with secinfo you will not have much problems.
After doing steps 4, 5 you can see rejected entries in Gateway log.