It's important to remember that 21 months is frequently too young for logical consequences. The perfect strategy for a child of two and a half or three will not work for a kidlet whose baby brain is still learning to process language. (See _Teaching With the Brain in Mind_, SECOND edition)
"Pitcher" is getting a lot of attention from his behavior. In Texas we can take kids to the park 12 months a year. Pitcher might need more outside, fresh air time (most high-motor boys do). Playing catch - 10 or 15 minutes at a time - could be a healthy outlet. However, what you really want is for Pitcher to stop throwing everything. You may not like this advice, but - quit returning anything he throws, and otherwise - ignore the throwing. If you can't duck, pretend it didn't hurt. Tippee cup? Give it to him for 10 - 30 seconds at a time, then move it out of reach. Back for another few seconds for the opportunity to have another sip before taking it out of reach again. Plastic everything. Throws food? Shower curtain under the high chair. He won't go hungry. No happy, healthy, well-adjusted chikd will starve him/herself. Kids this age live on air anyway. YOU WILL KNOW THAT YOU ARE ON THE RIGHT TRACK IF THE THROWING GETS WORSE. (It's called the Extinction Paradigm). Be strong, keep ignoring the inappropriate behavior and it really will go away. Pitcher's payoff is your reaction. No reaction? You remove the payoff. Of course, as a high-motor boy, he will try another way to bug you.
Of course, free advice is worth exactly what you pay for it. A little about me - mother of 4 (3 sons and a daughter), all now grown, public school teacher as my second career. Good luck!