Where did he go?

My son is two and an half. For the longest time I counted myself lucky that he didn't throw temper tantrums when we went out, that he would eat whatever I gave him and he was generally a good boy. I think I jinxed myself by telling someone and now he is a little monster. I am now the mom marching through the mall pushing the stroller and carrying a kicking, screaming, flailing toddler, with a huge grin on my face. I grin because I dare someone to say something. This kid is just unreal. If he is told not to jump on the couch, he'll continue to do it, even after I have exhausted every avenue of discipline and resorted to the very last effort: spanking. I never wanted to spank my kids, I vaguely remember being spanked and I definitely remember being terrified when I knew I was going to be spanked. The thing is, it doesn't really achieve much. My kid will still scream and kick at me when he wants his own way. He'll slap me in the face, push his sister down, refuse to sit in his chair to eat dinner etc. So what's a parent to do? I'm actually getting to the point where I don't want to take him anywhere which means I'll be house bound with three kids under 2 and will probably end up depressed. Oh, I forgot to mention that I made the insane decision to babysit a little boy. He's pretty good, other than he is the pickiest eater I have ever met and can be whiny and follows me around like a shadow. I really want my good boy back, I know he will get through this phase, but WHEN?!?!?!