On The Bit vs. Collection, and Where To Go From Here...
Due to a combination of things (namely mucho grande homework and a residential college an hour from home), I have only been able to work Scout a couple of times since I started the thread above. Well, I got to ride yesterday... .
I made a very conscious effort to sit up, mentally yelling at myself for tipping forward. I also focused a lot on my hands; getting my elbows back by my sides and my thumbs up, with just a few ounces' feel on the bit, my fingers more open than fists on the reins. The latter kind of miraculously followed the fixing of my elbows (yay!).
Scout did very well. Certainly no GP dressage outline, but much less of the "bird dog on scent" nose sticking out. While I focused on keeping my position more "classical," I worked Scout on his whoa/walk/trot transitions. By the end of the ride, he was responding instantly almost to my thought of changing gait!
I watched a Jane Savoie video on YouTube, and was really inspired by her demo of using your seat in either a passive/following, active/driving, or active/******ing fashion. My next step, I think is going to be researching and working on using my seat more effectively to maintain consistent rhythm within gaits, especially within Scout's trot, which can get lazy and rushy by turns.
Thanks to everyone for your wonderful advice! I am so grateful!