L.L.
I don't have a lot of advice, but I want to offer you some encouragement and empathy!! This is normal 2yr old behavior for boys. A mom of only a girl will not be as likely to understand the world of boys. And, let's not forget, a Mom of a 9 year old has pretty much completely forgotten the day-to-day struggles (and sometimes agony) of dealing with a 2 or 3 year old!!
You know...it's actually very healthy (and normal) that your son is testing these behaviors on you and not on others outside the home. You'll see this years down the road too....at Parent-Teacher conferences, your son's teachers will tell you what an intellegent, sweet boy you have and you will need to check if she's talking about the same kid! :) Your son's cognitive development and reasoning skills depend upon testing the rules. But you want him to test the rules in the safety of his own home...where he knows you will love him unconditionally no matter how much trouble he gets into. This shows you how powerful and "safe" your relationship really is!
Yes...you need to take breaks. I wish I had taken more breaks -- I think it would have made those "terrible 2s and 3s" years much more pleasant and enjoyable. Plus, it benefits your son to spend time with a loving relative or close, close friend. Take breaks -- and try to do it on a regular basis. Don't wait until those ocassions when you "can't take it any more." In summary: TAKE BREAKS!