One day at a time

Today was easier than yesterday for sure. I felt defeated and pushed to the limit by a three year old. We've been dealing with sibling rivalry for over a year and yesterday at lunch time I stepped outside while the children were in their chairs having lunch. A moment later I come back inside to see the baby in tears and the boy standing beside her. I asked why she was sad and he exclaimed with great joy "I'm hitting her!". That morning I had dealt out numerous time outs, explanations, heart-to-hearts and requested apologies over and over, only to hear he was now gaining pleasure from causing her pain and lapping up the attention. I took him directly to his room and told him how disappointed I was in his behavior with every muscle in my face and tone of my voice. I've never sounded or felt so firm, stern and angry. He knew something was different but still insisted on having jelly legs when I told him to sit on his bed. I told him to sit- he claimed he couldn't. My body was telling me to smack his bottom, my brain telling me not to. My body won. I hit his bottom for the first time- just once, but that was enough for him...and for me. My husband and I don't believe in spanking so it slipped past my better judgment to do so. He sat on his bottom and I told him to stay in time out. He did. After a few minutes I brought him some juice and told him to drink it and then lay down for nap. He said he wanted to talk and to apologize to his sister but I continued to tell him how disappointed I was in what he did; that its his job as a big brother to protect his sister from harm, especially when mommy is out of the room.
To make a long story a little less long, he stayed in his room for 45 minutes and then we went to playgroup. He had tons of energy at our friends house and was sent to time out for many poor decisions. I was feeling very down but the other moms tried offering suggestions which I was a dry sponge for.
I know he and I feed off each other's emotions. Today was a much better day because I had a better attitude about it. I made a pledge to myself to be proactive about this so we can both heal. I ordered a book for myself called Raising Your Child Not by Force but by Love which was recommended by a Natural Mama and a book for the boy called Hands are not for Hitting. I plan to create a responsibility chart to let him fulfill daily goals in order to receive a reward at the end of the week and I intend to spend more one on one time with him when the baby is sleeping. I moved his time out space to a corner in the living room instead or his room because I noticed he responded to it better during the time at our friend's home. I'm now using the timer on the microwave during time out so he can hear when three minutes is over. (We had a timer before and he loved it but it broke after a month or so and we never replaced it.) When he was sent to time out for hitting today, he stayed in the corner and didn't fuss. I know it's because he could see me. I think he just wanted to be a part of everything and know I wasn't going to abandon him. He needs to feel in control just as much as I do. He acts naughty to gain control of my attention and to feel powerful over his sister who takes my attention away from him. I get upset and yell, cuss, apparently hit because I'm losing control of myself and his respect. But, like I said, today was a better day. We made cookies together. I lay down with him at bedtime and said "I love you, angel." and he repeated it back.