SoSo it looks like I may be a more interesting case than I thought.
After everybody's feedback here, I looked more closely at my grip today and why everything was coming out nose-up. It turns out that (based on my wrist or shape of my hand or whatever) I can't use a power grip.
This is me trying to tilt my wrist as far down as I can get it with a power grip, while still leaving the disc in the crease of my hand. I had no hope of getting the nose down in flight. Add in the fact that most of the time I won't be able to tilt my wrist down even that far during an actual throw, and I had a real problem. I kept trying to maneuver my fingers around to get the disc angle further down, but nothing seemed to work.
Until I tried putting my index finger on the top, a.k.a. the Bonapane grip.
Finally I was able to actually keep the nose angle below the plane of my arm. I spent the rest of practice today trying to apply this new (to me) grip to my drive, and the results were immediate. I was regularly getting drives out to 290' without changing any of my other mechanics. I even managed to get one out to 330'; I've never come anywhere close to that on flat ground. And I gained some snap: I was able to flip my River all the way over from a hyzer angle into a roller (at 1:00).
Of course there were some inconsistencies, as you'd expect with a completely new grip, but it seems like I've found a winner. And that's with a ton of room for improvement in my footwork yet; I didn't want to change more than one thing at a time during one practice.
I guess the moral of the story for my fellow newbies is not to be completely wedded to one particular grip. It's worth trying others to see if they might work for you.