Well, you're right on point with your advice about the trade-in. Look 'em right in the eyes and lie like a rug. They're gonna lie to you, so why not? It is imperative however to know the accurate actual cash wholesale value of your trade, and negotiate to that point once you've gotten the real buying price of the new vehicle but not before then!
Do your best to keep emotion out of the transaction. They are pros, and can tell every time when you just gotta have it.
I would personally forget about trying to figure out what invoice is or is not. It really doesn't matter; they'll go only so low no matter what true cost is. And the floor manager likely doesn't really know anyway. There's the 2% "Holdback" you mention, as well as the quarterly incentives you again reference. True invoice is often difficult for even the dealer to figure. I know I got an honest $4000. off my $47000. sticker Limited in August, and that's enough for me. But I'm pretty sure they hated me when I left.
Whatever you do, remember that the only acceptable answer to any product offered in the F&I office is NO!!! PERIOD!! You can always buy the extended warranty later if you need it.
And finally, remember that your most important body part in this transaction is your feet. It's only when you get up to leave and they actually let you go that you can be sure you're really below their threshold of pain on the deal. Go back in and up your offer a hundred bucks at the time.
This entire procedure should be seen as war, and there most assuredly will not be two winners!