J.M.
I think we may have the same kid! We handle the tantrums by just walking away and have found that he won't hurt himself and doesn't like to perform without an audience. By not feeding into the tantrum, it deflates pretty quickly.
As far as the "no", I've found the same devilish grin on his face as he continues to do what I told him to stop doing. I remove his hand from whatever he shouldn't be playing in (usually the dog food storage container)with a firm, "NO" and redirect him to another activity or a toy that he can do - like a ball or puzzle.
I've found he gets into things and gives me the grin when I'm in the middle of something so it's an indicator that I need to stop what I'm doing for a minute and give him some attention. Of course with a pot boiling over on the stove, and the timer on the oven going off, this isn't always easy - but it's his way of saying, "mom, pay attention to me for a minute."