C.O.
Mommy,
Your son is 3. He is just barely understanding "good choices" - you need to keep your commands to his level and what he can understand.
He is NOT acting like a teenager - I have one - he's acting like a baby. He's regressing, in other words.
What is going on in your world?
Are you and your husband fighting?
Has his routine or schedule changed?
Did this just start recently - if so - can you rewind your memory to when this started and see what changes happened - it might help figure it out and get him back on the right track.
Hitting is not acceptable - however - he's learning it from somewhere. Whether someone is hitting him or he's seeing it. However, hitting is also something used in "toddlers" (and to me - an almost 4 year old is NOT a toddler) when they don't have the words to express their feelings.
When he is in time out? IGNORE him...even if he's hitting the wall - ignore him. He KNOWS what will set you off. he knows what will get you to run to him and give him attention. It doesn't sound like time out is working. So I would take all the toys away - ALL of them - and have him EARN them back with good behavior. Keep it simple. If he throws a toy - he doesn't get it back. He can USE HIS WORDS to express his frustration or feelings - NOT by hitting or throwing things.
If this continues? I would STRONGLY suggest you taking him to his pediatrician - and talk with the pediatrician - maybe there's something else going on and he needs intervention or further help!
Good luck!