Narkissos,
1. Is that limitation (to God's being the cause of events) the only one?
I spoke of no limitations that is your assumption. There are no limitations with God.
1.1. If so, what about natural catastrophes etc. (cf. Bradley's last post?)
Time and unforseen occurrences befall both man and beast. Or should man, the more intelligent creation, be coddled when he refuses to live according to the nature of things and goes so far as to recklessly live on known faultlines and to allow his fellow to live in shabby houses prown to earthquake damage and he refuses the expense of Tsunami warning systems but not the expense of war? If we wish to live as free men we must be responsible. If though, we wish to live as children being told how to eat and walk and live then we should all be JWs or cats and dogs.
Additionally, it is ironic that man who fails to raise all his own children to be productive and honest citizens not because he is incapable but because he is unwilling to spend the time and money, should at the same time fault God for man's own ills. Man's glass house is not God's fault it is man's.
2. Is that limitation absolute (God never has overruled any human will and never will?)
Again, God has no limitations.
2.1. If not, how is the limitation limited?
Again, God has no limitations.
3. Why does that limitation to God's causality exist in the first place?
Please see the answer above.
Sabrina