Its one of the things about meds that has always amazed me. You give a normal child a stimulant medicine and they start bouncing off the ceiling. You increase the dose and they go nuts. An ADHD child will slow down on the same med. And if the med is too much, they will zone out. Really kind of proves that they do have a medical condition and its just not bad parenting, etc. The sad thing is that the over medicating should not be happening. Either the Dr and parents are not communicating, or the Dr or the parent have just given up and taken the easy way out. It should not be happening. And it is correctable, but it does take some time and trial and error. All kids are different, and react differently.
You have got several things going on here. One, - he is a smart child who has learned how to manipulate (probably to protect himself). Two, he is highly frustrated. I have seen this happen a lot around 4th grade. The frustrations just build, and build and build. Until, he can learn how to deal with the frustrations (or they can be changed) - it will get worse. Three - he has a good case of ADHD. No filters, lack of concentration, etc.
I think that if you really understand what ADHD is and how it affects kids, you will have a better chance of helping him and feeling better about the whole situation.
A book I recommend a lot because it really answers a lot of your statements and questions is "The ADD/ ADHD Answer book," by Susan Ashley.
I think you will find my answer to this post helpful (and the post will ring a few bells). Checkout -
http://www.medhelp.org/posts/Child-Behavior/When-All-The-Typical-Rules-Dont-Work/show/1412667#post_6441834
At the bottom of my post I mention the site - http://www.healing-arts.org/children/ADHD/index.htm
Its worth checking out. It has a ton of information. So take your time. I kind of like the book a bit better because its easier to digest and its always handy.
Some other thoughts is that experts say it takes at least 3 weeks of consistent, immediate consequences (timeouts) for a behavioral change to take effect. It can take even longer with an adhd kid because they don't think before they act. However, as they get older (and 9 is about that point), they do start getting more control. The thing to keep in mind is that ADHD kids (when they are younger) really don't have very good filters. Hence they do things impulsively. It really doesn't take them very long (if they are intelligent) to figure out, that they are always getting blamed (probably correctly) by everyone and out of sheer survival instincts they lie. It happens all the time. Its not because of what you have done. Its because of what they have been experiencing for most of their life. Also sometimes, they do things so quickly (no filters) that they aren't really aware they even did it. So don't feel bad about his lies! Ignore it.
Finally, if you do decide to go the medicine route - do learn by your experiences with other kids. Pediatricians are kind of notorious for quickly medicating and not properly following up. If you do go that route, be very verbal about his meds and changes he is having. Don't be surprised to be getting the med changed every week or so until he hits the right dose. If you can - I would seek out a pediatric psychiatrist. You will have a much better chance of good communication.
Hope some of this helps. If you have any specific questions please post. I am sorry I took so long to get back to you.