W.W.
Your son needs the iPad TAKEN AWAY. PERIOD. He's six (6) years old. Not a toddler.
There is NO "CUT DOWN" time. IT MUST BE TAKEN AWAY. Your son needs to learn how to handle his emotions. Throwing something and hurting someone is NOT how it works. The question is WHERE is he learning that behavior from??
You will tell him today that because his behavior was unacceptable, he will no longer have access or be able to use the iPad for 2 weeks. You put it on the calendar. Don't make a big deal about it. Be matter of fact. Your behavior was unacceptable. You do NOT throw things nor hurt people because you don't like what was said or done. You have now lost the iPad for 2 weeks.
If he asks for it during that time frame? You tell him that if he asks for it again? It will be extended ANOTHER day. No means no. Actions have consequences. He can go outside and play. He can read a book. He can play games. No iPad. DO NOT GIVE IN. DO NOT compromise.
If it happens again? You will take ALL electronics away from him. If it happens again? I would also strongly suggest counseling on behavioral management.
Pay attention to how things are handled in the house. If daddy throws a fit? He's learning it from his dad. If daddy gets away with it? Then there is your problem and you must fix it. If you can't fix it? You demand counseling for the family on dealing with emotions and treating people better.