Need advice on my 6 y/o

I was just talking to DH and asked him if everyone has so many issues with their children, or do we just have bad luck? This time it is my 6 y/o. My 6 y/o has problems with controlling his impulses.....I know sounds so familiar. But he is different. Let me explain. This child is so loving, caring, and just such a pleasure to hang with, he has a wicked sense of humor and is so friendly, I just love him to pieces. He is soooo different from Noah in his personality. He is independent and so confident, he could be the life of a party. But he gets himself into so much trouble. He lacks natural limits on safety and is a wanderer. At 2 he wandered into out back woods when I ran into the house to grab the phone, the police came with dog sniffing dogs and he was found in the woods 4 houses down, which is very far from our house. He still talks about how the police man let him run the lights when he was driven home...good grief. He has been such a stressor for me, whenever we are out in public I have to keep my eyes on him at all times, he will disappear within seconds. He also steals in the house, he will go into the others kids rooms and steal toys and hide them, he steals money from my DHs change jar, and he also takes medications. About 6 mths ago he was vomiting and I just thought he was sick but it turned out that he took the allergy medication and drank it, they were sample sizes and I found them hidden all over the house. We started being very diligent again with locking the bathroom closet, we put a key lock on there a while back but it is quite inconvenient having it locked so we slacked off for a while. Well I found a pill in the toilet and he lied up and down blaming others and then finally after the threat that no one gets movies or dessert until some admits it, he then admitted to it. He went into our room while we were sleeping and took the key. He said he had a headache and needed medicine. It landed up being adult sudafed and thankfully he spit it out. This child scares me. I feel like we explain constantly to him that he can hurt himself and possibly even die if he takes too much, but it doesn't make any difference. I am calling the social worker at school, these people must just shake their heads when they hear it is me, what the heck is wrong with me and my family?????? In the meantime DH found a combination lock doorknob to put on our bedroom and that bathroom closet, he plans on picking them up today. We need a lock box for Noahs meds in the kitchen. My DH was looking at pistol lock boxes that have a combination lock, I don't feel like keys are safe around here. Anyone know of any other options for that? Thanks ladies, I hope I give back half of how much you all help me, I am thankful to have this board to turn to.