Other than using my chain of command, how can I rectify false statements on my NCOER?

First, they do not need to provide counseling to you for the missing U's, this is already documented through the unit sign-in roster and if your unit was on the ball they probably attempted to call you during the BTA and now have a record that will count against you regardless if you received a counseling or not.

I won't get into the nitty gritty as it sounds like you've already attempted to solve this at the lowest levels. Yes you can appeal, if you lose; nothing different happens NCOER is processed as usual. If you win great, you'll get another NCOER. Understand that the repeal process effects everyone in your rating chain, even if you do win I wouldn't expect high rating NCOER afterwards.

So the question is: Is it worth the fight? I see that your promoteable, will this NCOER cause you to lose your P status? typically not. HOWEVER if it truly will, then FIGHT. ultimately you are responsible for your own career. Is the overall Rating 'NOT-QUALIFIED'? If its not, lick your wounds and consider yourself lucky and do great things in the Army Reserves.

Not all leadership is equal, and some are downright mean. But there are always options, some better and others...

Actually, if there are no documents to prove the substandard ratings then you will probably automatically win that appeal. I would go for it. The failure of your support chain or rating scheme to do the paperwork benefits you.

NCOER's can be appealed all the way to DA. It takes paperwork and a lot of time. Never a sure thing, unless you can show they violated the regulation somehow.