I feel your pain. My 2 yo daughter has just started this as well since the birth of our son 10 weeks ago. We have read ALL the books tried to follow certain routines etc. but in the end i have found the main thing that makes her feral (technical term!) is when she a) hasnt had a good night time or day time sleep and b) has hardly eaten anything in typical toddler fashion.
so I have been making a super effort to watch what she eats but not make a fuss of it ie. put some pieces of fruit on her little table which she will pick at and hardly speak to her at the dinner table (we have found too much attention here makes it nearly impossible to get her to eat for some reason). Anyway, not sure if the diet and sleep and maybe exercise needs looking at in your sons case but thats just a few ideas. Then again, sometimes they are just feral just because........good luck!
Amy, mum of 2y.o. and 2 month old