1. I assume my best options if I want any chance of getting rid of this is to request a trial and request disclosure (is that what it's called? getting the officer notes, radar maintenance schedule etc?). What do I look for in all this? Assuming the ticket is without mistakes (I believe it is, but I'll double check tomorrow, it's at the office).
Correct. Request a trial and then when you receive your Notice of Trial, request disclosure. You can still have a trial without requesting disclosure, but it's not recommended.
As for stuff to look for, your options are pretty much endless. It would have to be something of significance that would prove you were not speeding. Calling your car "gray" when it's "gunmetal" is not something to build a case on.
Speeding is an absolute liability offense. It means you were speeding or you weren't. There's no in between. Definitely no "I was speeding, but...".
2. To request a trial, do I have to go to the courthouse, or do I just wait? It says to go to the courthouse on the ticket, but people are telling me just to wait.
Most tickets will let you submit a plea via mail. If that's not an option on your ticket, i'd suggest you follow the instructions on the back. Do not ignore it. It will be automatically entered as a guilty plea and you will be responsible for the fine. If you ignore the fine, your license will be suspended.
3. If I request a trial, get all the disclosure etc, and figure out I've no chance, up til what point can I still plead guilty to the reduced charge?
In almost all cases, you will receive a plea deal before your trial. Even if you had no defense, trials take up considerate amounts of time as all the steps of a trial need to take place. They would rather you plead guilty and move on. There will be more people showing up for trials afterwords and they can't have you occupying up all their time.
That being said, you are most likely not going to receive anything other than what you already have. You already had your ticket reduced from 21 over to 10 over (3 demerit points to 0). There just isn't anymore wiggle room there for you.
Should you go all the way to trial, your ticket will be brought back up to the original charge.
Also, if you're expecting the officer to not show up, the prosecution will sometimes hide whether they are in the building or not until you plea. Some prosecutors will drop the charges without you needing to do anything, others will play dumb until trial time. Either way it's not a regular occurrence or something to lean back on.
I asked x copper about it, and emailed a copy of the ticket on their request for more info, but I've heard nothing since...just to be sure; they can't just go about representing me without me signing something, right?
In all honesty, you're in a position where hiring an xcopper type service isn't going to benefit you much.