H.Z.
Wow...you have just described my oldest to a tee!! He is the most fun loving, passionate, smart individual...but also the most challenging. I am sorry to say that I have not found how to deal with him when he gets this way yet...but I am definitely actively working on it. I try not to yell (which takes a LOT of self control!!), and try and use positive reinforcements...but it is HARD!! When he is good he is the most amazing kid on the universe...when he is acting out he is a tyrant! I hope you get some good responses. Mine is just to say you aren't the only one!! Hang in there, you are doing an awesome job...and for a second time around...you should be commended.
Good luck! H. Z. (SAHM to 3 boys Spencer 5, James 4, and Wilco 17 months)