You need to try behavioral therapy. ADHD can be VERY hard on the parents but he needs to learn to control his explosive behavior. I would go to the library or buy a book about ADHD and read up on what he is going through and how to help him. Spanking will not help b/c it is likely that he doesn't know HOW to control these behaviors or HOW to respond in an appropriate manner. Seek therapy (many places can help for very little cost if that is an issue) and read up on how to communicate and help him learn to control his behavior. It isn't easy and takes awhile but my brother had it as a small child and is not he manager at a huge company and is doing very well.
I know how you feel, I think it's normal to want to run away from discord and bad kid behavior. Also, keep in mind, he may not be able to help it all the time either esp if he has a disorder. Did the neurologist provide any medications? Did they help?
If he is aggressive himself, I would stay away from the spanking, it can make the aggression worse. I foudn that with my son.
Just try to stay calm, if you need to, go into a room and shurt the door and take deep breaths. Do you ahve any family or friends that can help? If so, be sure that you can get some breaks. Are all the kids in school? How does your boy do in school/daycare?
Keep venting, it's important.... Just know there are others who are having issues too. You are not alone.