Not all what you said, but MOST of things matched, with my kid, when he was of that age. Now my kid is 4.2 and now it's just a couple of things do match up with my kid.
So, what do you get out of what I said.
Well, what I am trying to say is that you have to do some serious stuff here. First off, get the focus off from your kid, now being it's done, you get back your focus, have some faith, do some anger management, build up a very very good patience level. Carry a ton load of love. And now you being armed ready for the missionPOSSIBLE.
Task number 1: No matter what, never
ever spank him at this age. No eye harsh faces or eye goggling with anger. Take out his insecurity towards his sibling and Make him understand. No harsh speaking or yelling, at any point of time.
Task 2: Now as task 1 is under process, tackle the attention seeking issue. Believe me it's a very good sign, but he's unable to communicate. Make him understand that he has to earn (attention) by doing something worth, like saying a rhyme, doing a drawing etc. Tell him people around him, who loves a lot will feel hurt and sorry by his act of hitting, throwing things, yelling at, unreasonable crying to get things done his way. Now about the language / pronouncing, I believe it's not a issue at this age, but it'll be in later life. Try to teach him singing, slow and steady. Socializing? Just leave it. He'll get it sooner or later. Not a issue. Don't force him.
Task 3: Give alot off love and care. Don't talk to him negatively. Train yourself to be calm, even if you're going like nuts. Spend quality time him often. Sometimes let him be in a corner with whatever he likes to do, except colouring the walls. There's a lot to share and talk. But I've to go it's 4 morning. Have faith. Things will work out. What I am trying to say is: Usually all the kids will outgrow this. With lots of love and care. Hoping you like to know more.
PS: Things won't change overnight.