S.G.
Time out for that age shouldn't be anymore then a minute and half. Use a timer and let him watch it so he knows he isn't there forever. This will teach him to stay in time out without getting up, especially if you start the timer over again if he gets up. Time out really isn't time out when you are sitting with him. Then it becomes mommy and me time, so don't sit with him during time outs. My granddaughter hates time outs so she will straighten up with just the threat of one.
Hitting is normal for this age group. They dont have the communication skills to let their dislikes and frustrations be known in any other way. They are going to throw fits, hit or fight or scream to let you know they aren't happy. When you see him hit, go through the "we don't hit, it hurts other people" and the time out. Also give him words to use now that he is starting to talk or will be shortly. After the time out tell him "I know you are Angry, but you can't hurt people when you are angry" Make sure you give him a hug and kiss after the time out so he knows you love him. I also told my granddaughter when she would hit me "Grandma doesn't like to be hit... she likes hugs and kisses much more" Now when she wants to hit, she thinks twice and will give me hugs and kisses instead. She is 21 months old. I also know with my granddaughter that if she gets to the stage of hitting, it usually means she is getting really tired and is acting out for that reason. I usually try to get her down for her nap around that time. I don't do it as a punishment and tell her "I see you are getting tired by the way you are acting, lets lay down for a bit" She might fight it but I tell her "your eyes are saying 'oh Emma, please let me rest' and your body is saying 'Oh, Emma, we need to sleep so we will feel better and be happier'". I also sing a song that I made up "you're a sleepy girl, you're a sleepy girl, close your eyes, close your eyes, you are very tired, you are very tired, go to sleep go to sleep" She goes to sleep with that song just to get me to stop singing, I think.
Consistancy and patience is what is needed for this age group. Good luck.